Gerrit git cl: make it work with minimal file.

BUG=656555
R=emso@chromium.org,andybons@chromium.org

Review-Url: https://codereview.chromium.org/2421253002
diff --git a/git_cl.py b/git_cl.py
index a61bb91..d8b9004 100755
--- a/git_cl.py
+++ b/git_cl.py
@@ -3064,7 +3064,8 @@
     else:
       RunGit(['config', '--unset-all', fullname], error_ok=unset_error_ok)
 
-  SetProperty('server', 'CODE_REVIEW_SERVER')
+  if not keyvals.get('GERRIT_HOST', False):
+    SetProperty('server', 'CODE_REVIEW_SERVER')
   # Only server setting is required. Other settings can be absent.
   # In that case, we ignore errors raised during option deletion attempt.
   SetProperty('cc', 'CC_LIST', unset_error_ok=True)