xenconfig: change 'hap' setting to align with Xen behavior

hap is enabled by default in xm and xl config and usually only
specified when it is desirable to disable hap (hap = 0). Change
the xm,xl <-> xml converter to behave similarly. I.e. only
produce 'hap = 0' when <hap state='off'/> and vice versa.

Signed-off-by: Jim Fehlig <jfehlig@suse.com>

tests/xlconfigtest.c

@@ -213,6 +213,7 @@ mymain(void)
     DO_TEST("spice");
     DO_TEST("spice-features");
     DO_TEST("vif-rate");
+    DO_TEST("fullvirt-nohap");
 
     DO_TEST("paravirt-cmdline");
     DO_TEST_FORMAT("paravirt-cmdline-extra-root");