Terminate gpg-agent after each test.

This is actual for gnupg 2.1 that requires the agent and starts it
automatically. But since each test creates a new keystore tests become
fail after the first one starts gpg-agent.

tests/integration/minion/test_pillar.py

@@ -237,6 +237,19 @@ class DecryptGPGPillarTest(ModuleCase):
 
     @classmethod
     def tearDownClass(cls):
+        cmd = ['gpg-connect-agent', '--homedir', GPG_HOMEDIR]
+        try:
+            log.debug('Killing gpg-agent using: %s', cmd)
+            output = subprocess.Popen(cmd,
+                                      stdin=subprocess.PIPE,
+                                      stdout=subprocess.PIPE,
+                                      stderr=subprocess.STDOUT,
+                                      shell=False).communicate(input=six.b('KILLAGENT'))[0]
+            log.debug('Result:\n%s', output)
+        except OSError:
+            log.debug('No need to kill: old gnupg doesn\'t start the agent.')
+            pass
+
         if cls.created_gpg_homedir:
             try:
                 shutil.rmtree(GPG_HOMEDIR)