virt-log: do_log_journal: return instead of exiting immediately.

This cleans up commit a3475cf9bbbbd3514b117d5edd75d9c0e239d43a.
virt-log: Add support for displaying the Windows Event Log.

Uses the external program python-evtx, and this only works
for Windows >= Vista.
tests/guests: Add new file debian-syslog to EXTRA_DIST.

This fixes commit 026342a7ee20cd31d4de6c212e848791f7099d5e.
Version 1.27.17.