init: hide identify spam when reinitializing

We don't want to keep showing the user config notice when reinitializing
existing checkouts, so hide it.

Change-Id: Id40610bd683396cbff7e1aefc092c8b77c397783
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/343536


Tested-by: Mike Frysinger <vapier@google.com>
Reviewed-by: LaMont Jones <lamontjones@google.com>