Most of our code base uses space after comma but not before;
fix the remaining uses before adding a syntax check.

* tests/sysinfotest.c: Consistently use commas.
* tests/viratomictest.c: Likewise.
* tests/vircgroupmock.c: Likewise.
* tools/virsh-domain.c: Likewise.
* tools/virsh-volume.c: Likewise.
Signed-off-by: NEric Blake <eblake@redhat.com>