cifs: add check for returning value of SMB2_close_init

If the returning value of SMB2_close_init is an error-value,
exit the function.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 352d96f3

 ("cifs: multichannel: move channel selection above transport layer")

Signed-off-by: Anastasia Belova <abelova@astralinux.ru>
Signed-off-by: Steve French <stfrench@microsoft.com>