recipe engine: remove explicit cwd default in step recipe module

recipe_modules/shutil/example.expected/basic.json

Index: recipe_modules/shutil/example.expected/basic.json
diff --git a/recipe_modules/shutil/example.expected/basic.json b/recipe_modules/shutil/example.expected/basic.json
index 58a06c26be206974b54679818f5307b6678c78c9..d5168913b5ac21d394716ea9f5df48f2b12bc4fe 100644
--- a/recipe_modules/shutil/example.expected/basic.json
+++ b/recipe_modules/shutil/example.expected/basic.json
@@ -6,7 +6,6 @@
       "\nimport os\nimport sys\nos.remove(sys.argv[1])\n",
       "bar"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "foo",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@python.inline@@@@",
@@ -24,7 +23,6 @@
       "/fake/dir",
       "/path/to/tmp/json"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "listdir fake dir",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@json.output@[@@@",
@@ -45,7 +43,6 @@
       "some",
       "command"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "manipulate file 1"
   },
   {
@@ -53,7 +50,6 @@
       "some",
       "command"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "manipulate file 2"
   },
   {
@@ -61,7 +57,6 @@
       "echo",
       "[TMP_BASE]/prefix_a_tmp_1"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "print prefix_a"
   },
   {
@@ -69,7 +64,6 @@
       "echo",
       "[TMP_BASE]/prefix_b_tmp_2"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "print prefix_b"
   },
   {
@@ -80,7 +74,6 @@
       "abcde",
       "tmp_file.txt"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "write_simple"
   },
   {
@@ -91,7 +84,6 @@
       "tmp_file.txt",
       "/path/to/tmp/"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "read_simple"
   },
   {
@@ -102,7 +94,6 @@
       "! ~&&",
       "tmp_file.txt"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "write_symbols"
   },
   {
@@ -113,7 +104,6 @@
       "tmp_file.txt",
       "/path/to/tmp/"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "read_symbols"
   },
   {
@@ -124,7 +114,6 @@
       "abcde fgh",
       "tmp_file.txt"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "write_spaces"
   },
   {
@@ -135,7 +124,6 @@
       "tmp_file.txt",
       "/path/to/tmp/"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "read_spaces"
   },
   {
@@ -146,7 +134,6 @@
       "ab\ncd\nefg\n",
       "tmp_file.txt"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "write_multiline"
   },
   {
@@ -157,7 +144,6 @@
       "tmp_file.txt",
       "/path/to/tmp/"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "read_multiline"
   },
   {
@@ -168,7 +154,6 @@
       "[SLAVE_BUILD]/copytree_example_tmp",
       "511"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "makedirs makedirs",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@python.inline@@@@",
@@ -191,7 +176,6 @@
       "some file content",
       "[SLAVE_BUILD]/copytree_example_tmp/dummy_file"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "write [SLAVE_BUILD]/copytree_example_tmp/dummy_file"
   },
   {
@@ -203,7 +187,6 @@
       "[SLAVE_BUILD]/copytree_example_tmp2",
       "0"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "copytree"
   },
   {
@@ -214,7 +197,6 @@
       "[SLAVE_BUILD]/copytree_example_tmp2/dummy_file",
       "/path/to/tmp/"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "read [SLAVE_BUILD]/copytree_example_tmp2/dummy_file"
   },
   {
@@ -225,7 +207,6 @@
       "/path/to/tmp/",
       "[SLAVE_BUILD]/copytree_example_tmp/*"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "glob"
   },
   {
@@ -235,7 +216,6 @@
       "\nimport shutil, sys\nshutil.rmtree(sys.argv[1])\n",
       "[SLAVE_BUILD]/copytree_example_tmp"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "cleanup",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@python.inline@@@@",
@@ -251,7 +231,6 @@
       "\nimport shutil, sys\nshutil.rmtree(sys.argv[1])\n",
       "[SLAVE_BUILD]/copytree_example_tmp2"
     ],
-    "cwd": "[SLAVE_BUILD]",
     "name": "cleanup2",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@python.inline@@@@",