Maybe something like this.
Warning: I have not actually tested it.
--- a/debian/control
+++ b/debian/control
@@ -154,7 +154,8 @@ Replaces: libdcerpc-server0 (<< 2:4.0.9),
libsamdb0 (<< 2:4.0.9),
libsmbclient-raw0 (<< 2:4.0.9),
libsmbd0 (<< 2:4.0.9),
- libtorture0 (<< 2:4.0.9)
+ libtorture0 (<< 2:4.0.9),
+ samba (<< 2:4.2.10+dfsg-0+deb8u2)
# these conflicts can NOT be replaced by 'Breaks'
# the old 3.6 packages should be removed before the new samba-libs is
# unpacked, to avoid any code referencing the old location of the tdb files
