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