gcm_run.j doesn't exit on fail

[mathomp4]

Per @Dooruk (see GEOS-ESM/swell#643), gcm_run.j doesn't seem to return an exit on fail. I can see this is at least true for the model part. For example:

@NATIVE_BUILD @OCEAN_PRELOAD @SEVERAL_TRIES $RUN_CMD $TOTAL_PES $GEOSEXE $IOSERVER_OPTIONS $IOSERVER_EXTRA --logging_config 'logging.yaml'

if( $USE_SHMEM == 1 ) $GEOSBIN/RmShmKeys_sshmpi.csh >& /dev/null

if( -e EGRESS ) then
   set rc = 0
else
   set rc = -1
endif
echo GEOSgcm Run Status: $rc

A few things.

1. There is no exit here. If EGRESS is not found, we should actually exit!
2. For shells, -1 is not a valid/recognized exit status.
3. If EGRESS isn't found, the echo doesn't matter.