Remove Xen get hostname driver method

The xenGetHostname entry point in the xenUnifiedDriver table
was unused.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

src/xen/xen_driver.h

@@ -93,7 +93,6 @@ extern int xenRegister (void);
  * structure with direct calls in xen_unified.c.
  */
 struct xenUnifiedDriver {
-    virDrvConnectGetHostname xenGetHostname;
     virDrvDomainGetMaxMemory xenDomainGetMaxMemory;
     virDrvDomainSetMaxMemory xenDomainSetMaxMemory;
     virDrvDomainSetMemory xenDomainSetMemory;