When bin/drydock lease is interrupted, release leases

Summary:
Depends on D19072. Ref T13073. Currently, you can leave leases stranded by using `^C` to interrupt the script. Handle signals and release leases on destruction if they haven't activated yet.

Also, print out more useful information before and after activation.

Test Plan: Mashed ^C while runnning `bin/drydock lease ... --trace`, saw the lease release.

Subscribers: yelirekim, PHID-OPKG-gm6ozazyms6q6i22gyam

Maniphest Tasks: T13073

Differential Revision: https://secure.phabricator.com/D19073

scripts/init/init-script-with-signals.php

@@ -0,0 +1,11 @@
+<?php
+
+// Initialize a script that will handle signals.
+
+if (function_exists('pcntl_async_signals')) {
+  pcntl_async_signals(true);
+} else {
+  declare(ticks = 1);
+}
+
+require_once dirname(__FILE__).'/init-script.php';