cifs: make sure we ignore the credentials= and cred= options
Older mount.cifs programs passed this on to the kernel after parsing
the file. Make sure the kernel ignores that option.
Should fix:
https://bugzilla.kernel.org/show_bug.cgi?id=43195
Cc: Sachin Prabhu <sprabhu@redhat.com> Reported-by: Ronald <ronald645@gmail.com> Signed-off-by: Jeff Layton <jlayton@redhat.com> Signed-off-by: Steve French <sfrench@us.ibm.com>