Forget last daemon/ dir artefacts

The most important part is LIBVIRTD_PATH env var fix. It is used
in virFileFindResourceFull() from tests. The libvirtd no longer
lives under daemon/.

Then, libvirtd-fail test was still failing (as expected) but not
because of missing config file but because it was trying to
execute (nonexistent) top_builddir/daemon/libvirtd which
fulfilled expected outcome and thus test did not fail.

Thirdly, lcov was told to generate coverage for daemon/ dir too.

Fourthly, our compiling documentation was still suggesting to run
daemonn/libvirtd.

And finally, some comments in a systemtap file and a probes file
were still referring to daemon/libvirtd.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: John Ferlan <jferlan@redhat.com>

tests/libvirtd-fail

@@ -5,12 +5,12 @@
 
 if test "$VERBOSE" = yes; then
   set -x
-  $abs_top_builddir/daemon/libvirtd --version
+  $abs_top_builddir/src/libvirtd --version
 fi
 
 fail=0
 
-$abs_top_builddir/daemon/libvirtd --config=no-such-conf --timeout=5 2> log
+$abs_top_builddir/src/libvirtd --config=no-such-conf --timeout=5 2> log
 RET=$?
 
 test "$RET" != "0" && exit 0 || exit 1