output timing information for repo sync's
output timing information for repo sync's

Via the upgrade to 1.7.8.1, we gained a --time option; this can be used
to get the real time of any subcommand executed.  Thus include some basic
timing information.

BUG=None
TEST=cbuildbot x86-generic-full

Change-Id: If711ee3172fd5090e3b2426665c0cff1f2c96e26
Reviewed-on: https://gerrit.chromium.org/gerrit/13567
Tested-by: Brian Harring <fdc2d0a2e2340b623587cee5ea8dff425d1eb1f3@chromium.org>
Reviewed-by: Chris Sosa <959d3d631fb6f17f1b07f751372041a1edb210d1@chromium.org>
Commit-Ready: Brian Harring <fdc2d0a2e2340b623587cee5ea8dff425d1eb1f3@chromium.org>

zhang0137/chromite,zhang0137/chromite,chadversary/chromiumos.chromite,bpsinc-native/src_third_party_chromite,chadversary/chromiumos.chromite,bpsinc-native/src_third_party_chromite,coreos/chromite,bpsinc-native/src_third_party_chromite,coreos/chromite,zhang0137/chromite,coreos/chromite