[milo] remove linkBase and calculate links directly.

milo/buildsource/swarming/expectations/build-exception.json

Index: milo/buildsource/swarming/expectations/build-exception.json
diff --git a/milo/buildsource/swarming/expectations/build-exception.json b/milo/buildsource/swarming/expectations/build-exception.json
index 110465b07f272a100c0bed0c42e4f1f557d902a2..5fddb1938e3a4e4ac1d961cf79d242bdc502de4a 100644
--- a/milo/buildsource/swarming/expectations/build-exception.json
+++ b/milo/buildsource/swarming/expectations/build-exception.json
@@ -16,7 +16,7 @@
       [
         {
           "Label": "stdout",
-          "URL": "foo/stdout"
+          "URL": "/swarming/task/build-exception/stdout"
         }
       ]
     ],
@@ -39,7 +39,7 @@
       "MainLink": [
         {
           "Label": "stdout",
-          "URL": "foo/steps/recipe_bootstrap/0/stdout"
+          "URL": "/swarming/task/build-exception/steps/recipe_bootstrap/0/stdout"
         }
       ],
       "Started": "2016-03-14T10:00:02Z",
@@ -56,14 +56,14 @@
       "MainLink": [
         {
           "Label": "stdout",
-          "URL": "foo/steps/setup_build/0/stdout"
+          "URL": "/swarming/task/build-exception/steps/setup_build/0/stdout"
         }
       ],
       "SubLink": [
         [
           {
             "Label": "run_recipe",
-            "URL": "foo/steps/setup_build/0/logs/run_recipe/0"
+            "URL": "/swarming/task/build-exception/steps/setup_build/0/logs/run_recipe/0"
           }
         ]
       ],
@@ -83,14 +83,14 @@
       "MainLink": [
         {
           "Label": "stdout",
-          "URL": "foo/steps/bot_update/0/stdout"
+          "URL": "/swarming/task/build-exception/steps/bot_update/0/stdout"
         }
       ],
       "SubLink": [
         [
           {
             "Label": "json.output (invalid)",
-            "URL": "foo/steps/bot_update/0/logs/json.output__invalid_/0"
+            "URL": "/swarming/task/build-exception/steps/bot_update/0/logs/json.output__invalid_/0"
           }
         ]
       ],
@@ -108,14 +108,14 @@
       "MainLink": [
         {
           "Label": "stdout",
-          "URL": "foo/steps/Uncaught_Exception/0/stdout"
+          "URL": "/swarming/task/build-exception/steps/Uncaught_Exception/0/stdout"
         }
       ],
       "SubLink": [
         [
           {
             "Label": "exception",
-            "URL": "foo/steps/Uncaught_Exception/0/logs/exception/0"
+            "URL": "/swarming/task/build-exception/steps/Uncaught_Exception/0/logs/exception/0"
           }
         ]
       ],