ecore/main: only update loop_time during loop iteration if the change is monotonic

ecore/main: only update loop_time during loop iteration if the change is monotonic

Summary:
in the case where the user has called loop_time_set with a value in the future,
avoid setting the loop time to something that would potentially cause a callback
to occur with a loop_time value before a previous occurrence of that callback

@fix

Reviewers: ManMower

Reviewed By: ManMower

Subscribers: ManMower, #reviewers, cedric, #committers

Tags: #efl_main_loop

Differential Revision: https://phab.enlightenment.org/D6764