test: Create common state directories for temporary files

The test scripts create a bunch of temporary files to keep track of
internal state.  Some are made in /tmp with individual mktemp calls, some
go in the passt source directory, and some go in $LOGDIR.  This can
sometimes make it messy to clean up after failed test runs.

Start cleaning this up by creating a single "state" directory ($STATEBASE)
in /tmp for all the state or temporary files used by a single test run.
Clean it up automatically in cleanup() - except when DEBUG==1, because
those files can be useful for debugging test script failures.

We create subdirectories under $STATEBASE for each setup function, exposed
as $STATESETUP.  We also create subdirectories for each test script and
expose those to the scripts as __STATEDIR__.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

test/lib/setup

@@ -394,6 +394,8 @@ teardown_demo_podman() {
 # $*:	Suffix list of setup_*() functions to be called
 setup() {
 	for arg do
+		STATESETUP="${STATEBASE}/${arg}"
+		mkdir -p "${STATESETUP}"
 		eval setup_${arg}
 	done
 }