Fix disabling of apparmor/selinux security drivers

When using --without-$name --without-secdriver-$name with $name being
selinux or apparmor, configure will fail saying that AppArmor/SELinux
development package must be installed.
This is caused by a small bug in --with-secdriver-$name handling in
configure.ac which treats --without-secdriver-$name when $name as if the
user had requested to enable $name when $name couldn't be detected on
the system.

This commit also makes sure the detection checks for disabled
secdrivers do not needlessly get run, especially as this could
cause an error as well in --with-$name --without-secdriver-$name
situations.

configure.ac

@@ -1493,10 +1493,11 @@ AC_ARG_WITH([secdriver-selinux],
 if test "$with_selinux" != "yes" ; then
   if test "$with_secdriver_selinux" = "check" ; then
     with_secdriver_selinux=no
-  elif test "$with_secdriver_selinux" = "yes"; then
+  fi
+  if test "$with_secdriver_selinux" != "no"; then
         AC_MSG_ERROR([You must install the libselinux development package and enable SELinux with the --with-selinux=yes in order to compile libvirt --with-secdriver-selinux=yes])
   fi
-else
+elif test "$with_secdriver_selinux" != "no"; then
   old_cflags="$CFLAGS"
   old_libs="$LIBS"
   CFLAGS="$CFLAGS $SELINUX_CFLAGS"
@@ -1571,10 +1572,11 @@ AC_ARG_WITH([secdriver-apparmor],
 if test "$with_apparmor" != "yes" ; then
   if test "$with_secdriver_apparmor" = "check" ; then
     with_secdriver_apparmor=no
-  else
+  fi
+  if test "$with_secdriver_apparmor" != "no" ; then
     AC_MSG_ERROR([You must install the AppArmor development package in order to compile libvirt])
   fi
-else
+elif test "with_secdriver_apparmor" != "no" ; then
   old_cflags="$CFLAGS"
   old_libs="$LIBS"
   CFLAGS="$CFLAGS $APPARMOR_CFLAGS"