After switching to filesystem context support, we no longer need to
handle mount options string when chasing dfs referrals.  Now, we set
the new values directly into smb3_fs_context.

Start working on a separate source file to handle most dfs related
mount functions as connect.c has already became too big.  The
remaining functions will be moved gradually in follow-up patches.
Signed-off-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Signed-off-by: Steve French <stfrench@microsoft.com>