charon-cmd: Block SIGUSR1 on worker threads

To properly shut down charon-cmd with leak reports, only the main thread
should catch SIGUSR1 to shut down the application. Work threads should ignore
SIGUSR1 to avoid any hard application termination.

src/charon-cmd/charon-cmd.c

@@ -389,6 +389,7 @@ int main(int argc, char *argv[])
 	sigaddset(&action.sa_mask, SIGINT);
 	sigaddset(&action.sa_mask, SIGTERM);
 	sigaddset(&action.sa_mask, SIGHUP);
+	sigaddset(&action.sa_mask, SIGUSR1);
 	sigaction(SIGSEGV, &action, NULL);
 	sigaction(SIGILL, &action, NULL);
 	sigaction(SIGBUS, &action, NULL);