V8 Buildbot: Add the ability to disable tests in nosnap mode.

scripts/slave/recipes/v8.expected/full_client_v8_V8_Linux___nosnap___debug.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "[DEPOT_TOOLS]/gclient.py",
       "config",
       "--spec",
       "cache_dir = None\nsolutions = [{'custom_deps': {'v8/test/mozilla/data': 'svn://svn-mirror.golo.chromium.org/chrome/trunk/deps/third_party/mozilla-tests'}, 'deps_file': 'DEPS', 'managed': True, 'name': 'v8', 'url': 'http://v8.googlecode.com/svn/branches/bleeding_edge'}]"
     ],
@@ skipping 86 matching lines @@
     "cmd": [
       "python",
       "-u",
       "[BUILD]/scripts/slave/v8/v8testing.py",
       "--target",
       "Debug",
       "--arch",
       "ia32",
       "--testname",
       "mjsunit cctest message preparser",
+      "--no-snap",
       "--flaky-tests",
       "skip"
     ],
     "cwd": "[SLAVE_BUILD]/v8",
     "name": "Check",
     "seed_steps": [
       "Check",
       "Check - flaky",
       "Test262",
       "Mozilla"
     ]
   },
   {
     "abort_on_failure": false,
     "cmd": [
       "python",
       "-u",
       "[BUILD]/scripts/slave/v8/v8testing.py",
       "--target",
       "Debug",
       "--arch",
       "ia32",
       "--testname",
       "mjsunit cctest message preparser",
+      "--no-snap",
       "--flaky-tests",
       "run"
     ],
     "cwd": "[SLAVE_BUILD]/v8",
     "name": "Check - flaky"
   },
   {
     "cmd": [
       "python",
       "-u",
       "[BUILD]/scripts/slave/v8/v8testing.py",
       "--target",
       "Debug",
       "--arch",
       "ia32",
       "--testname",
-      "test262"
+      "test262",
+      "--no-snap"
     ],
     "cwd": "[SLAVE_BUILD]/v8",
     "name": "Test262"
   },
   {
     "cmd": [
       "python",
       "-u",
       "[BUILD]/scripts/slave/v8/v8testing.py",
       "--target",
       "Debug",
       "--arch",
       "ia32",
       "--testname",
-      "mozilla"
+      "mozilla",
+      "--no-snap"
     ],
     "cwd": "[SLAVE_BUILD]/v8",
     "name": "Mozilla"
   }
 ]