Fixed add_key stalling indefinitely, and test code leaking into production setting

library/apt_key

@@ -105,7 +105,7 @@ def download_key(url):
 
 
 def add_key(key):
-    return call("apt-key add -", shell=True, stdin=PIPE, stdout=PIPE, stderr=PIPE)
+    p = Popen("apt-key add -", shell=True, stdin=PIPE, stdout=PIPE, stderr=PIPE)
     (_, _) = p.communicate(key)
 
     return p.returncode == 0