Use sync bind for searching, needed by MS AD

[steffenschumacher]

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?

Fixes #1193

PS. complete newbie in python/ldap/nipap, so please don't shoot me :/

[webminster]

Why has this never been merged (or similar merged)? I had this exact issue in current codebase, and had to change it locally to work.
-Alan

[steffenschumacher]

I think this project is next to abandoned I’m afraid.
I did actually nearly complete a port to py3.6, but never completed it due to lack of time, but since the authors aren’t active anymore I’m migrating to something else soonish..