vz: build driver as module and don't register it on client's side

Make it possible to build vz driver as a module and don't link it with
libvirt.so statically.
Remove registering it on client's side as far as we start relying on daemon

Signed-off-by: Maxim Nestratov <mnestratov@virtuozzo.com>

daemon/Makefile.am

@@ -233,6 +233,10 @@ if WITH_VBOX
     libvirtd_LDADD += ../src/libvirt_driver_vbox.la
 endif WITH_VBOX
 
+if WITH_VZ
+    libvirtd_LDADD += ../src/libvirt_driver_vz.la
+endif WITH_VZ
+
 if WITH_STORAGE
     libvirtd_LDADD += ../src/libvirt_driver_storage.la
 endif WITH_STORAGE