nmci: Add '@RHEL-nnn' tag for linking of RHEL-nnn issues in RH Jira

The tag is used in analogous way to the @rhbznnn tags for RHBZ bugs:

@rhbz123456 @RHEL-1234
@scen_name
Scenario: long name
Given ...
When ...
Then ...

resulting in clickable link in the html report to: i.r.c/browse/RHEL-nnn

Existing comments with RH Jira references are converted to the tags.