Fix INTERNAL_OBJ error on stop when calendars.conf missing

Initialize the calendars container before calling load_config and return FAILURE
on allocation failure. Also, use the AST_MODULE_LOAD_* values for return values.
Thanks to rmudgett for pointing out the error and the need to use the defined
values for return


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@242812 65c4cc65-6c06-0410-ace0-fbb531ad65f3