Allow drive.file clientaccess scope

todrive actions for reports often only need to create drive files, not read
other files. drive.file scope limits GAM to being able to create files and
read just those files.

src/gam/gamlib/glapi.py

@@ -499,6 +499,10 @@ _TODRIVE_CLIENT_SCOPES = [
    'api': DRIVE3,
    'subscopes': [],
    'scope': DRIVE_SCOPE},
+  {'name': 'Drive File API - todrive_clientaccess',
+   'api': DRIVE3,
+   'subscopes': [],
+   'scope': 'https://www.googleapis.com/auth/drive.file'},
   {'name': 'Gmail API - todrive_clientaccess',
    'api': GMAIL,
    'subscopes': [],