sync: merge project updates with status bar

The current sync output displays "Fetching project" and "Checking out
project" messages and progress bar updates independently leading to a
lot of spam.  Lets merge these periodic outputs with the status bar to
get a little bit tighter output in the normal case.  This doesn't solve
all our problems, but gets us closer.

Bug: https://crbug.com/gerrit/11293
Change-Id: Icd627830af4dd934a9355b7ace754b56dc96cfef
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/244934
Reviewed-by: David Pursehouse <dpursehouse@collab.net>
Tested-by: Mike Frysinger <vapier@google.com>