Foreman » Installer

Fixes #33765 - Use a system user without a login shell

The user pulp doesn't need to login so it's set to /sbin/nologin.

It should also be a system user. This doesn't affect exsting
installations, but it ensures fresh installations are clean. From
useradd's man page:

System users will be created with no aging information in
    /etc/shadow, and their numeric identifiers are chosen in the
    SYS_UID_MIN-SYS_UID_MAX range, defined in /etc/login.defs, instead
    of UID_MIN-UID_MAX (and their GID counterparts for the creation of
    groups).

This typically means newly created pulp users will end up with a UID <
1000 while with the current code it's > 1000.