fix "disabling echoes and oplocks" on SMB2 mounts

SMB2 and later will return only 1 credit for session setup (phase 1)
not just for the negotiate protocol response.  Do not disable
echoes and oplocks on session setup (we only need one credit
for tree connection anyway) as a resonse with only 1 credit
on phase 1 of sessionsetup is expected.

Fixes the "CIFS VFS: disabling echoes and oplocks" message
logged to dmesg.

Signed-off-by: Steve French <smfrench@gmail.com>
Acked-by: Jeff Layton <jlayton@samba.org>