This is a reland of 3774c589

Added missing options.enforce_fetch arg

Confirmed via a fake test roll with this CL's patch commit that the
bot_update step passes with this change:
https://chromium-review.googlesource.com/c/chromium/tools/build/+/2443649

Original change's description:
> Reland "Add optional enforce_fetch kwarg to fetch and refresh git cache"
>
> This is a reland of f38f54f2
>
> Original change's description:
> > Add optional enforce_fetch kwarg to fetch and refresh git cache
> >
> > Allows builders to do a force refresh of the git cache to ensure a new
> > fetch happens. android-binary-size needs this to get an accurate diff
> > of the passed in src revision and the applied patch:
> > https://bugs.chromium.org/p/chromium/issues/detail?id=1129235#c19
> >
> > Bug: 1129235
> > Change-Id: I993521cdde2a491fc9d42d75ff28dedcd2cea64e
> > Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2438802
> > Commit-Queue: Stephanie Kim <kimstephanie@google.com>
> > Reviewed-by: Josip Sokcevic <sokcevic@google.com>
>
> Bug: 1129235
> Change-Id: I034a91a8b57821d08b10042f7fc94d32350540ba
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2443235
> Reviewed-by: Edward Lesmes <ehmaldonado@chromium.org>
> Commit-Queue: Stephanie Kim <kimstephanie@google.com>

Bug: 1129235
Change-Id: Ibbd4535f8529243d2dc1d4d32881d8a61efe374a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2443574Reviewed-by: Josip Sokcevic <sokcevic@google.com>
Commit-Queue: Stephanie Kim <kimstephanie@google.com>