cifs: avoid race conditions with parallel reconnects

cifs: avoid race conditions with parallel reconnects

[ Upstream commit bc962159e8e326af634a506508034a375bf2b858 ]

When multiple processes/channels do reconnects in parallel
we used to return success immediately
negotiate/session-setup/tree-connect, causing race conditions
between processes that enter the function in parallel.
This caused several errors related to session not found to
show up during parallel reconnects.

Signed-off-by: Shyam Prasad N <sprasad@microsoft.com>
Reviewed-by: Paulo Alcantara (SUSE) <pc@manguebit.com>
Cc: stable@vger.kernel.org
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>