server+sambaDC: temporarily rollback libtalloc

This should be reverted ASAP but as of today #31881 holds:
- samba-DC 4.3.6 + libtalloc 2.1.6 break `samba-tool domain provision';
- samba-DC 4.3.6 + libtalloc 2.1.5 won't build [1];
- samba-DC 4.3.5 + libtalloc 2.1.5 work (but have known vulnerabilities).

[1] using p7 archive packages, rebuilding 4.3.6 with 2.1.5 should help

pkg.in/lists/tagged/server+sambaDC

@@ -1,3 +1,15 @@
-task-samba-dc
+task-samba-dc=4.3.5
+
+python-module-samba-DC=4.3.5
+samba-DC-common=4.3.5
+samba-DC-winbind-clients=4.3.5
+samba-DC-winbind=4.3.5
+samba-DC=4.3.5
+samba-DC-client=4.3.5
+samba-DC-doc=4.3.5
+samba-DC-libs=4.3.5
+libpytalloc=2.1.5
+libtalloc=2.1.5
+
 bind-utils
 tdb-utils