Also adds unit tests for the SSSDConfig API

This should fix #218
It should also prevent us from leaking memory in case the original request times
out and should prevent races with the callbacks beeing freed after sdp_req is
freed and thus dereferencing freed memory in the callbacks detructors.

Always use the network timeout defined in the options.
But raise defaults to 60 seconds or enumerations can easily fail.

Loop control variable was not being incremented.
I also converted a goto loop into a do...while loop to make it
easier to follow the logic.

Update gettext strings