Gclient sometimes ignores "unmanaged": "False" in the gclient solution
if --revision <anything> is passed.  This forces gclient to always
treat solutions deps as unmanaged.

BUG=693296

Change-Id: I91d5f4c9377fab0fde23cf15d1475779978820fa
Reviewed-on: https://chromium-review.googlesource.com/444098
Commit-Queue: Andrii Shyshkalov <tandrii@chromium.org>
Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>