'injected_files' should be base 64 encoded.

If an instance build needs to be rescheduled, send the original
base 64 encoded injected_files parameter.

bug 1161479

Change-Id: I4dad95e95cd27f7f128989daa36b3a2bbf132c73
Merge "'injected_files' should be base 64 encoded."
Merge remote-tracking branch 'm_src_repo/master' into build-temp