cifs: add a smb2_compound_op and change QUERY_INFO to use it

This turns most open/query-info/close patterns in cifs.ko
to become compounds.

This changes stat from using 3 roundtrips to just a single one.

Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>