cros_merge_to_branch: add cherry pick tip for commit message
cros_merge_to_branch: add cherry pick tip for commit message

I have to look up the command for re-using a failed cherry pick message.
I suspect I'm not the only one.  Include it in the tips section for easy
reference.

BUG=None
TEST=`cros_merge_to_branch '*32765' R25 --nowipe` included right message

Change-Id: Ie158d0b12bfb090024a84880ee1e556567e96bde
Reviewed-on: https://gerrit.chromium.org/gerrit/43735
Reviewed-by: Chris Sosa <959d3d631fb6f17f1b07f751372041a1edb210d1@chromium.org>
Commit-Queue: Mike Frysinger <8f3f75c74bd5184edcfa6534cab3c13a00a2f794@chromium.org>
Tested-by: Mike Frysinger <8f3f75c74bd5184edcfa6534cab3c13a00a2f794@chromium.org>

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