libxbps: require a pointer to xbps_handle in functions that need it.

This removes 2 global vars from lib/initend.c and easier to know
what functions require access to xbps_handle.

bin/xbps-bin/check_pkg_symlinks.c

@@ -45,9 +45,11 @@
  * returns 0 if test ran successfully, 1 otherwise and -1 on error.
  */
 int
-check_pkg_symlinks(const char *pkgname, void *arg, bool *pkgdb_update)
+check_pkg_symlinks(struct xbps_handle *xhp,
+		   const char *pkgname,
+		   void *arg,
+		   bool *pkgdb_update)
 {
-	const struct xbps_handle *xhp = xbps_handle_get();
 	prop_array_t array;
 	prop_object_t obj;
 	prop_object_iterator_t iter;