Allow metadata updates to provider resources

If the metadata of a provider resource changes, we shouldn't replace the
whole provider.

This is not a backport, because this has been fixed more generically for
all resources in master, where update_allowed_properties no longer
exists.

Change-Id: I706b3a2faeef582e906fe2195d79200ab3853a2c
Closes-Bug: #1332354
Merge "Allow metadata updates to provider resources" into stable/icehouse