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

t/lib-gpg.sh

@@ -31,6 +31,7 @@ then
 		chmod 0700 ./gpghome &&
 		GNUPGHOME="$(pwd)/gpghome" &&
 		export GNUPGHOME &&
+		(gpgconf --kill gpg-agent 2>&1 >/dev/null || : ) &&
 		gpg --homedir "${GNUPGHOME}" 2>/dev/null --import \
 			"$TEST_DIRECTORY"/lib-gpg/keyring.gpg &&
 		gpg --homedir "${GNUPGHOME}" 2>/dev/null --import-ownertrust \