Cloned from https://bugzilla.redhat.com/show_bug.cgi?id=1461194

Description of problem:

A couple of users have expressed interest in a "host list only" API. This would be useful when scripting and looping over lots of hosts. If it took the same params as the existing /hosts api but returned only the host ID and hostname, that would be ideal.

There are a performance issues with the existing /hosts API call that are being addressed¹; however even if it was lightning fast, a more minimal result set is still useful for scripting.

This is similar to Spacewalk's listActiveSystems call² which does not return system details. The RFE came about from users with spacewalk scripts that run much slower after porting to Katello.

[1] https://bugzilla.redhat.com/show_bug.cgi?id=1445623
[2] http://www.spacewalkproject.org/documentation/api/2.3/handlers/SystemHandler.html#listActiveSystems