Add additional virsh command line completion functions
Mentor: Michal Privoznik @MichalPrivoznik
Completers are small functions that are called from the virsh command line tool whenever the user started typing something and hit TAB TAB. Their purpose is to offer list of strings that suit entered input. If there is only one item on the list then it's entered in automatically. For instance:
virsh # dom<TAB><TAB>
domblkerror domblkstat domcontrol domfsinfo ..
virsh # start --domain <TAB><TAB>
fedora fedora.i686 freebsd gentoo ...
Additional functions are needed to improve other commands.
An example patch:
https://www.redhat.com/archives/libvir-list/2018-June/msg01672.html
A series of example patches:
https://www.redhat.com/archives/libvir-list/2018-January/msg00436.html