The QEMU command line arguments are very long and currently all written
on a single line to /var/log/libvirt/qemu/$GUEST.log. This introduces
logic to add line breaks after every env variable and "-" optional
argument, and every positional argument. This will create a clearer log
file, which will in turn present better in bug reports when people cut +
paste from the log into a bug comment.

An example log file entry now looks like this:

  2018-12-14 12:57:03.677+0000: starting up libvirt version: 5.0.0, qemu version: 3.0.0qemu-3.0.0-1.fc29, kernel: 4.19.5-300.fc29.x86_64, hostname: localhost.localdomain
  LC_ALL=C \
  PATH=/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin \
  HOME=/home/berrange \
  USER=berrange \
  LOGNAME=berrange \
  QEMU_AUDIO_DRV=none \
  /usr/bin/qemu-system-ppc64 \
  -name guest=guest,debug-threads=on \
  -S \
  -object secret,id=masterKey0,format=raw,file=/home/berrange/.config/libvirt/qemu/lib/domain-33-guest/master-key.aes \
  -machine pseries-2.10,accel=tcg,usb=off,dump-guest-core=off \
  -m 1024 \
  -realtime mlock=off \
  -smp 1,sockets=1,cores=1,threads=1 \
  -uuid c8a74977-ab18-41d0-ae3b-4041c7fffbcd \
  -display none \
  -no-user-config \
  -nodefaults \
  -chardev socket,id=charmonitor,fd=23,server,nowait \
  -mon chardev=charmonitor,id=monitor,mode=control \
  -rtc base=utc \
  -no-shutdown \
  -boot strict=on \
  -device qemu-xhci,id=usb,bus=pci.0,addr=0x1 \
  -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x2 \
  -sandbox on,obsolete=deny,elevateprivileges=deny,spawn=deny,resourcecontrol=deny \
  -msg timestamp=on
  2018-12-14 12:57:03.730+0000: shutting down, reason=failed
Signed-off-by: NDaniel P. Berrangé <berrange@redhat.com>