Exam - Multiselect does not work for filters

[ser-popov]

Repro Steps:

1. Login as an Examiner
2. Use the Type column filter to select to show only Strata
3. Use the filter to show both Strata and Hosts

Actual:
See screenshot
The system does not show any of the Hosts, only Strata

Expected:
If multiple options are possible, system should show the union of both sets
If not possible, option should not be available to user (single select only)