Description of problem:
Singular is used instead of plural even when operating with multiple hosts.

Version-Release number of selected component (if applicable):
6.8

How reproducible:
always

Steps to Reproduce:
1. Navigate to the Content Hosts page.
2. Select multiple hosts whose services require a reboot.
3. Select "Manage Host Traces" from the actions list.
4. Select multiple entries that require a reboot on multiple hosts.
5. Click on the "Restart Selected" button.

Actual results:
"Resolving the selected Traces will reboot this host." is displayed in the window.

Expected results:
There should be a plural used - "hosts" not "host" if you selected Traces on multiple hosts.

Additional info:
Created during the verification of BZ1709557.

Katello code:
https://github.com/jturel/katello/blob/d5ce8e0809cb9080b968e1e0b8c5b145af87cd01/engines/bastion_katello/app/assets/javascripts/bastion_katello/content-hosts/content/views/content-host-traces.html#L46