V8 Buildbot: Fix side effect problem in V8 factory.
V8 Buildbot: Fix side effect problem in V8 factory.

Makes now a copy of the factory_properties just like in chromium factory to avoid side effects.

Review URL: https://chromiumcodereview.appspot.com/19007003

git-svn-id: 239fca9b83025a0b6f823aeeca02ba5be3d9fd76@211353 0039d316-1c4b-4281-b951-d872f2087c98

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