configure: fix typo in nss error message

This error message refers to the lack of network, not to yajl.
Signed-off-by: NPino Toscano <ptoscano@redhat.com>

m4/virt-nss.m4

@@ -37,7 +37,7 @@ AC_DEFUN([LIBVIRT_CHECK_NSS],[
 
     if test "x$with_network" != "xyes" ; then
       if test "x$with_nss_plugin" = "xyes" ; then
-        AC_MSG_ERROR([Can't build nss plugin without yajl])
+        AC_MSG_ERROR([Can't build nss plugin without network])
       else
         with_nss_plugin=no
       fi