Make sure the nrfds and nefds are reset to NULL

before we enter manage_parkinglot.
This will get rid of CLI warnings like:
__ast_read: Exception flag set on 'SIP/<NUMBER>-<ID>', but no exception handler

(closes issue #12748)
Reported by: nreinartz
Patches:
      asterisk-multiparking_initialize_filedescr_sets-0.0.1.patch uploaded by nreinartz (license 452)


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@119015 65c4cc65-6c06-0410-ace0-fbb531ad65f3