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/xmconfigdata/test-fullvirt-nohap.cfg

@@ -0,0 +1,28 @@
+name = "XenGuest2"
+uuid = "c7a5fdb2-cdaf-9455-926a-d65c16db1809"
+maxmem = 579
+memory = 394
+vcpus = 1
+pae = 1
+acpi = 1
+apic = 1
+hap = 0
+viridian = 0
+rtc_timeoffset = 0
+localtime = 0
+on_poweroff = "destroy"
+on_reboot = "restart"
+on_crash = "restart"
+device_model = "/usr/lib/xen/bin/qemu-dm"
+sdl = 0
+vnc = 1
+vncunused = 1
+vnclisten = "127.0.0.1"
+vncpasswd = "123poi"
+vif = [ "mac=00:16:3e:66:92:9c,bridge=xenbr1,script=vif-bridge,model=e1000" ]
+parallel = "none"
+serial = "none"
+builder = "hvm"
+kernel = "/usr/lib/xen/boot/hvmloader"
+boot = "d"
+disk = [ "phy:/dev/HostVG/XenGuest2,hda,w", "file:/root/boot.iso,hdc:cdrom,r" ]