fix(test): eliminate false positives from is-microvm-dead check

Ensure that `ps(1)` does not truncate the command, which might result in
the grep failing (if the jailer_id gets truncated), using the -ww
option. While we're at it, also use -o cmd so that ps only prints the
command names and nothing else (as we're not using anything else from
this output).

This causes false-positives instead of false-negatives funnily enough,
because we're using check_output, meaning if the grep doesnt find
anything we fail the command (in the "everything works" scenario,
firecracker is dead but grep still matches the "ps | grep" process
itself).

Signed-off-by: Patrick Roy <roypat@amazon.co.uk>

Author: roypat

tests/framework/microvm.py

@@ -330,7 +330,7 @@ def kill(self):
 
             # filter ps results for the jailer's unique id
             _, stdout, stderr = utils.check_output(
-                f"ps aux | grep {self.jailer.jailer_id}"
+                f"ps ax -o cmd -ww | grep {self.jailer.jailer_id}"
             )
             # make sure firecracker was killed
             assert (