CI: Add optional patch level, fix hostname on F42

In the past there have been times when we need to generate new RPMs
for an existing ZFS release. Typically this happens when a new RHEL
version comes out and the kernel symbols no longer match. To get
users to auto-update we just bump the patch number. For example, we
had to create zfs-2.1.13-1 for EL8.8 and zfs-2.1.13-2 for EL8.9.

This commit adds an optional patch level text box to the github
package builder runner.

In addition, this commit also uses hostnamectl instead of hostname
for F42+ compatibility, if available.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Tony Hutter <hutter2@llnl.gov>
Closes #17638