Merge branch 'st/lib-gpg-kill-stray-agent' into maint

Some versions of GnuPG fails to kill gpg-agent it auto-spawned and such a left-over agent can interfere with a test. Work it around by attempting to kill one before starting a new test. * st/lib-gpg-kill-stray-agent: t: lib-gpg: flush gpg agent on startup