When a user type Control-C to interrupt gpg operation (when pinentry-curses
dialog is active), gpg should shutdown pinentry gracefully.
Configure gpg-agent with pinentry-curses, minimum test case is:
$ gpg --sign some.txt [Type Control-C, when you see curses dialog]
The pinentry process won't be killed by Control-C (because it doesn't have
Expected behavior is when gpg cancels its operation, it should notify
gpg-agent so that gpg-agent can cancel pinentry.