Totara - support completion via RPL

[danmarsden]

We need to add support for COMPLETION_COMPLETE_RPL to the Totara branches in the function reengagement_check_target_completion()

https://github.com/catalyst/moodle-mod_reengagement/blob/TOTARA_12/lib.php#L800

[danmarsden]

hmm - this might not be the full picture... the comments in Totara 12 codebase related to that setting state:
TOTARA: This isn't used anywhere in Totara, and hasn't since 2.2.0 at least, so we're going to
// remove it after the release of Totara 10.

I do suspect the code needs updating to get Totara's completion state correctly though.