Increase test-gnupg-collection timeout

Patch from Debian, originally by Emilio Pozuelo Monfort.

The timeout length in the current test is too low and can make the test fail if the system is too slow or too loaded. This test correctly stops waiting when a result is received, so the timeout will not actually be reached unless there is a problem.

[smcv: Expand commit message]
Fixes: #29 (closed)
Bug-Debian: https://bugs.debian.org/846728