[bot_update] Resolve revision only if patching

If bot_update is not patching, it shouldn't look into gitiles patch
information.

R=ehmaldonado@google.com

Bug: 1147625
Recipe-Nontrivial-Roll: build
Change-Id: I111f0dc1c36d588341c02930bf1cda1f5b8cc2e7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2644199
Reviewed-by: Edward Lesmes <ehmaldonado@chromium.org>
Commit-Queue: Josip Sokcevic <sokcevic@google.com>

recipes/recipe_modules/bot_update/api.py

@@ -240,8 +240,8 @@ class BotUpdateApi(recipe_api.RecipeApi):
       fixed_revision = self.m.gclient.resolve_revision(revision)
       if fixed_revision:
         fixed_revisions[name] = fixed_revision
-        if fixed_revision.upper() == 'HEAD':
-          # Sync to correct destination ref if HEAD was specified.
+        if fixed_revision.upper() == 'HEAD' and patch:
+          # Sync to correct destination ref
           fixed_revision = self._destination_ref(cfg, name)
         # If we're syncing to a ref, we want to make sure it exists before
         # trying to check it out.