Fix "atest --skylab" to upload CLs to configured remote name.

Fix InventoryRepo.upload_change to get git remote from
inventory-repo-dir and upload CLs to the git remote.

BUG=chromium:845708
TEST="atest server mod" with "--skylab"

Change-Id: I41f9bd46c4c1c120cb9f04359443f679b47ed181
Reviewed-on: https://chromium-review.googlesource.com/1067756
Commit-Ready: ChromeOS CL Exonerator Bot <[email protected]>
Tested-by: Ningning Xia <[email protected]>
Reviewed-by: Prathmesh Prabhu <[email protected]>
diff --git a/cli/topic_common.py b/cli/topic_common.py
index 8a1d333..e6acf6f 100644
--- a/cli/topic_common.py
+++ b/cli/topic_common.py
@@ -465,7 +465,10 @@
                                dest='environment',
                                default='prod')
         self.parser.add_option('--inventory-repo-dir',
-                               help=('The path to clone skylab inventory repo. '
+                               help=('The path of directory to clone skylab '
+                                     'inventory repo into. It can be an empty '
+                                     'folder or an existing clean checkout of '
+                                     'infra_internal/skylab_inventory.'
                                      'If not provided, a temporary dir will be '
                                      'created and used as the repo dir.'
                                      'Only useful when --skylab is enabled'),