V8 Buildbot: Refactor test configuration in V8 recipe.
V8 Buildbot: Refactor test configuration in V8 recipe.

This removes a bit boilerplate from the builder configuration.

BUG=315202

Review URL: https://codereview.chromium.org/198853007

git-svn-id: 239fca9b83025a0b6f823aeeca02ba5be3d9fd76@257952 0039d316-1c4b-4281-b951-d872f2087c98

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