Avoid pm-is-supported spam in logs

Per the libvirt team, the only way to stop the spam in
libvirtd logs is to install pm-utils package. Details are in:

https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/994476

Closes-Bug: #1274772
Closes-Bug: #1297512

Change-Id: Ia2f7a388470dcd8a3e2c12cf2980beccd65af94c
Fix typos in HACKING.rst

Two trivial fixes. One makes a broken external link work, the other
completes consistent casing (Devstack -> DevStack).

Change-Id: I147a3c5fe72071e9ebf24e7f226ba01a0a1204e3
Merge "Avoid pm-is-supported spam in logs"