launch: libvirt: Clarify comment.
launch: If launch takes longer than 20 minutes, time out.

Add a constant fixed timeout for launch (currently 20 minutes, we'll
make it configurable if needed in the future).  If the appliance takes
longer than this to connect back, we time out assuming that the kernel
has hung during boot.
df: parallel: Add a debug message when work function returns an error.

Further attempts to find out why this hangs under Koji.
builder: Upload /etc/resolv.conf from the host when the network is enabled.

When the user has enabled the network (not the default) we upload
/etc/resolv.conf from the host to the appliance /etc/resolv.conf
so that programs in the appliance can contact nameservers.

Commit 9521422ce60578f7196cc8b7977d998159238c19 previously changed the
behaviour to copy /etc/resolv.conf into the sysroot when running
commands.
Update TODO with more ideas.