Use sync bind for searching, needed by MS AD

With my corp MS AD, I get:
00002024: LdapErr: DSID-0C0605D4, comment: No other operations may be performed on the connection while a bind is outstanding., data 0, v1db1
without the '_s', and it works with it - if this is intentionally async, then it should be configurable I think?

PS. complete newbie in python/ldap/nipap, so please don't shoot me :/