PARAM_NUMBER is a float, our id's are int's

* Fix core_cohort_get_cohorts to specify correct return type on cohort id
* Fix core_enrol_get_enrolled_users_with_capability to specify correct
  correct return type on user id
* Fix core_cohort_update_cohorts to specify the right parameter type
  (int) on cohort id
* Add tests to verify the bug on core_cohort_update_cohorts param type.

Previously, even when a specific setting had to be returned, this method
would return an empty array. Now, the behaviour is the same whether
some options or none are set: if the requested setting is not found
null is returned.

MDL-40354 groups:groups_get_activity_allowed_groups() should use passed userid to check capabilities

Merge branch 'm26_MDL-39832_Fix_Chrome_Issues_ETag_XSendfile_2ndRound' of https://github.com/scara/moodle

Conflicts:
	lib/deprecatedlib.php