agent: Fix leak in CockpitFakeManager when cancelled
agent: Fix leak in CockpitRestJson one per watch
daemon: Fix several leaks in machines code

Change to a better array for pointers and actually free the
array among other things.
websocket: Fix a couple leaks in WebSocket code

Were leaking all headers for each initial socket request
ws: Fix leak of login password bytes
ws: Fix a couple leaks in CockpitHandlers code

Were leaking hostname and a struct for each login request
ws: Fix leak of per HTTP request structure
ws: Fix a couple of leaks in CockpitWebService code
Fix leaks in various unit tests

These let us get a clean bill of health on definite leaks
Add leak checking for definite leaks to 'make check-memory'