cifs: add cifs_sb_master_tcon and convert some callers to use it

At mount time, we'll always need to create a tcon that will serve as a
template for others that are associated with the mount. This tcon is
known as the "master" tcon.

In some cases, we'll need to use that tcon regardless of who's accessing
the mount. Add an accessor function for the master tcon and go ahead and
switch the appropriate places to use it.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
diff --git a/fs/cifs/readdir.c b/fs/cifs/readdir.c
index 3efc242..887a7e2 100644
--- a/fs/cifs/readdir.c
+++ b/fs/cifs/readdir.c
@@ -102,7 +102,7 @@
 		return NULL;
 	}
 
-	if (cifs_sb_tcon(CIFS_SB(sb))->nocase)
+	if (cifs_sb_master_tcon(CIFS_SB(sb))->nocase)
 		dentry->d_op = &cifs_ci_dentry_ops;
 	else
 		dentry->d_op = &cifs_dentry_ops;
@@ -171,7 +171,7 @@
 cifs_std_info_to_fattr(struct cifs_fattr *fattr, FIND_FILE_STANDARD_INFO *info,
 		       struct cifs_sb_info *cifs_sb)
 {
-	int offset = cifs_sb_tcon(cifs_sb)->ses->server->timeAdj;
+	int offset = cifs_sb_master_tcon(cifs_sb)->ses->server->timeAdj;
 
 	memset(fattr, 0, sizeof(*fattr));
 	fattr->cf_atime = cnvrtDosUnixTm(info->LastAccessDate,