Don't pass namespace name in disable_isolated_metadata_proxy

Don't pass namespace name in disable_isolated_metadata_proxy

It's not always possible/convenient to get namespace name
when need to disable some process (like metadata process for stale
router, see related bug). Since namespace name is not required
for process manager to disable process we can remove this parameter
from disable_isolated_metadata_proxy()

Change-Id: I0e0da01d9640aa9920f41989804fc6f320c1c1eb
Related-Bug: #1455042