fix VNC SASL detection

This test was missing the change to != no.

Signed-off-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

configure

diff --git a/configure b/configure
index 618e4dc..863bf58 100755
--- a/configure
+++ b/configure
@@ -1000,7 +1000,7 @@
 
 ##########################################
 # VNC SASL detection
-if test "$vnc_sasl" = "yes" ; then
+if test "$vnc_sasl" != "no" ; then
   cat > $TMPC <<EOF
 #include <sasl/sasl.h>
 #include <stdio.h>