Fix the mapping test in continuous

It turns out that due to a recent gdm change, the inherited
signal mask has SIGUSR1 blocked - which is bad news for
tests using SIGUSR1. Fix the test by explicitly checking the
signal mask before using SIGUSR1.
Fix the closure test in continuous

This test has the same problem as the mapping-test - it uses
SIGUSR1 without checking the signal mask. Apply the same fix
here.