Implement --no-autocc flag for Gerrit

R=ehmaldonado@chromium.org, machenbach@chromium.org

Bug: 878303
Change-Id: Ic387bbdc9e8ee4b27b17505ca53e8873e20e4cda
Reviewed-on: https://chromium-review.googlesource.com/1238571
Reviewed-by: Edward Lesmes <ehmaldonado@chromium.org>
Commit-Queue: Sergiy Byelozyorov <sergiyb@chromium.org>

git_cl.py

@@ -3152,7 +3152,7 @@ class _GerritChangelistImpl(_ChangelistCodereviewBase):
     reviewers = sorted(change_desc.get_reviewers())
 
     # Add cc's from the CC_LIST and --cc flag (if any).
-    if not options.private:
+    if not options.private and not options.no_autocc:
       cc = self.GetCCList().split(',')
     else:
       cc = []