cifs: reduce warning log level for server not advertising interfaces

Several users have reported this log getting dumped too regularly to
kernel log. The likely root cause has been identified, and it suggests
that this situation is expected for some configurations
(for example SMB2.1).

Since the function returns appropriately even for such cases, it is
fairly harmless to make this a debug log. When needed, the verbosity
can be increased to capture this log.

Cc: stable@vger.kernel.org
Reported-by: Jan Čermák <sairon@sairon.cz>
Signed-off-by: Shyam Prasad N <sprasad@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>