Correctly use defined return values in (some) load_module functions.

(issue #11096)
Patches:
      chan_agent.c.patch uploaded by eliel (license 64)
      chan_local.c.patch uploaded by eliel (license 64)
      chan_features.c.patch uploaded by eliel (license 64)
      chan_zap.c.patch uploaded by eliel (license 64)
      res_monitor.c.patch uploaded by eliel (license 64)
      res_realtime.c.patch uploaded by eliel (license 64)
      res_crypto.c.patch uploaded by eliel (license 64)


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@87202 65c4cc65-6c06-0410-ace0-fbb531ad65f3