Remove incorrect reference to args no longer available

Remove attempt to get 'upstream_commit' arg and instead rely on the
arguments that have already been passed to ImportUpstream at creation
time.

Remove unnecessary use of getattr and retrieve option values directly
from the args variable.

Change-Id: Ib8a6b0ec271778b3f18f3e71b085f95e01edd68e

ghp/commands/import_upstream.py

@@ -336,11 +336,8 @@ def do_import_upstream(args):
     strategy = ImportStrategiesFactory.createStrategy(args.strategy,
                                                       branch=args.branch)
 
-    commit = getattr(args, 'upstream_commit', None) or args.upstream_branch
     logger.notice("Starting import of upstream")
-    importupstream.create_import(commit,
-                                 checkout=getattr(args, 'checkout', None),
-                                 force=getattr(args, 'force', None))
+    importupstream.create_import(force=args.force)
     logger.notice("Successfully created import branch")
 
     importupstream.start(strategy)