Remove rev-parse --verify FETCH_HEAD

It's not used and causes some problems if refs on clone aren't set
properly.

R=ehmaldonado@chromium.org

Bug: 1049610
Change-Id: I71c1215c9a3355dd54e2d66860d755c6fe8032db
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2224853Reviewed-by: Edward Lesmes <ehmaldonado@chromium.org>
Commit-Queue: Josip Sokcevic <sokcevic@google.com>

gclient_scm.py

@@ -1327,9 +1327,6 @@ class GitWrapper(SCMWrapper):
       fetch_cmd.append('--quiet')
     self._Run(fetch_cmd, options, show_header=options.verbose, retry=True)
 
-    # Return the revision that was fetched; this will be stored in 'FETCH_HEAD'
-    return self._Capture(['rev-parse', '--verify', 'FETCH_HEAD'])
-
   def _SetFetchConfig(self, options):
     """Adds, and optionally fetches, "branch-heads" and "tags" refspecs
     if requested."""

subprocess2.py

@@ -200,6 +200,8 @@ def call(args, **kwargs):
   Automatically convert stdout=PIPE or stderr=PIPE to VOID.
   In no case they can be returned since no code path raises
   subprocess2.CalledProcessError.
+
+  Returns exit code.
   """
   if kwargs.get('stdout') == PIPE:
     kwargs['stdout'] = VOID