Fix CrOS tryjob verification
Fix CrOS tryjob verification

Not specifying optional values were incorrectly treated as an error.

BUG=None
TEST=Test not specifying option val.

Review URL: http://codereview.chromium.org/9720015

git-svn-id: 239fca9b83025a0b6f823aeeca02ba5be3d9fd76@127315 0039d316-1c4b-4281-b951-d872f2087c98

eunchong/build,eunchong/build,eunchong/build,eunchong/build