scripts: loman: Fix finding enabled_groups

We split the output of `git config` and the last item will contain '\n'.
Strip the output first.

BUG=None
TEST=(1) git config -f /mnt/host/source/.repo/manifests.git/config \
           --get manifest.groups
     (2) It outputs `minilayout,platform-linux`.
     (3) loman add --workon chromiumos/platform/factory
     (4) With this CL, it outputs
         `minilayout,platform-linux,name:chromiumos/platform/factory`.
     (5) Without this CL, it outputs
         `minilayout,platform-linux,platform-linux
,name:chromiumos/platform/factory`

Change-Id: I27da900deae9669582e9ea372831badde9ec4c2a
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/3686113
Commit-Queue: Cheng Yueh <cyueh@chromium.org>
Tested-by: Cheng Yueh <cyueh@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
diff --git a/scripts/loman.py b/scripts/loman.py
index 8fb41f6..5f34ee9 100644
--- a/scripts/loman.py
+++ b/scripts/loman.py
@@ -78,7 +78,7 @@
   git_config = options.git_config
 
   cmd = ['config', '-f', git_config, '--get', 'manifest.groups']
-  enabled_groups = git.RunGit('.', cmd, check=False).output.split(',')
+  enabled_groups = git.RunGit('.', cmd, check=False).output.rstrip().split(',')
 
   # Note that ordering actually matters, thus why the following code
   # is written this way.