[SDK] Fix script to assign yaml_file via command line

yaml_file variable is not passed to pkg_yaml_file in def
UploadSdkPackage, this CL fixes that bug.

Bug: 659808
Change-Id: I20fb5ca685993f540b4b4699ed5ebdc006e636ff
Reviewed-on: https://chromium-review.googlesource.com/848293
Reviewed-by: John Budorick <jbudorick@chromium.org>
Commit-Queue: Shenghua Zhang <shenghuazhang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#527054}

tools/android/sdk_updater/update_sdk.py

@@ -200,10 +200,9 @@ def UploadSdkPackage(sdk_root, dry_run, service_url, package, yaml_file,
     pkg_version: The version of the package instance.
     verbose: Enable more logging.
   """
-  if not yaml_file:
-    pkg_yaml_file = os.path.join(sdk_root, 'cipd_%s.yaml' % package)
-    if not os.path.exists(pkg_yaml_file):
-      raise IOError('Cannot find .yaml file for package %s' % package)
+  pkg_yaml_file = yaml_file or os.path.join(sdk_root, 'cipd_%s.yaml' % package)
+  if not os.path.exists(pkg_yaml_file):
+    raise IOError('Cannot find .yaml file for package %s' % package)
 
   if dry_run:
     print 'This `package` command (without -n/--dry-run) would create and',