ws: complete g_autoptr() usage in main()
ws: complete g_autoptr() usage in main()

We already use g_autoptr() in cockpit-ws, but had to exclude a couple of
cases because of missing support for those types.

Make use of g_autoptr() for those types as well, now.

This change also fixes a very small leak in an error case.

deryni/cockpit,moraleslazaro/cockpit,mvollmer/cockpit,garrett/cockpit,cockpituous/cockpit,garrett/cockpit,martinpitt/cockpit,garrett/cockpit,deryni/cockpit,cockpit-project/cockpit,deryni/cockpit,deryni/cockpit,mvollmer/cockpit,deryni/cockpit,cockpituous/cockpit,cockpit-project/cockpit,cockpituous/cockpit,mvollmer/cockpit,martinpitt/cockpit,garrett/cockpit,moraleslazaro/cockpit,martinpitt/cockpit,moraleslazaro/cockpit,cockpituous/cockpit,mvollmer/cockpit,deryni/cockpit,martinpitt/cockpit,mvollmer/cockpit,martinpitt/cockpit,cockpit-project/cockpit,moraleslazaro/cockpit,garrett/cockpit,cockpituous/cockpit,moraleslazaro/cockpit,moraleslazaro/cockpit,moraleslazaro/cockpit,deryni/cockpit,cockpit-project/cockpit,cockpituous/cockpit,cockpit-project/cockpit