Cleanup the updated sys limits capability. Fix a few copy/paste bugs (my bad). Shift the limit set to the ODLS default module so that we sete the limits for all apps, even those that don't call opal_init. Leave it in opal_init as well to support direct-launch apps, but ensure we only set the limits once by removing the envar after launch by ODLS.

Provide some nice error messages if we fail to set the limits. Since the user had to specifically request we set the limit, treat failure as an error-out situation.