* Fix a logic error in configure.ac that prevented --with-selinux=no
  from being used with --with-secdriver-selinux=no.

* Fix some strings to clarify the difference between --with-selinux
  and --with-secdriver-selinux.
Signed-off-by: NSpencer Shimko <sshimko@tresys.com>
Signed-off-by: NEric Blake <eblake@redhat.com>