Fixed virGetUNIXSocketPath stub on Win32

The _() macro was not terminated and an argument needs to be marked as
unused.
Signed-off-by: NDaniel P. Berrangé <berrange@redhat.com>

src/util/virutil.c

@@ -2014,10 +2014,10 @@ char *virGetUNIXSocketPath(int fd)
 
 #else /* HAVE_SYS_UN_H */
 
-char *virGetUNIXSocketPath(int fd)
+char *virGetUNIXSocketPath(int fd ATTRIBUTE_UNUSED)
 {
     virReportSystemError(ENOSYS, "%s",
-                         _("UNIX sockets not supported on this platform");
+                         _("UNIX sockets not supported on this platform"));
     return NULL;
 }