Merge ~hloeung/layer-snap:master into ~stub/layer-snap:master

[Haw Loeung]

Overriding snapd proxy via /etc/systemd/system/snapd.service.d/* also works in Trusty - LP:1533899

[Stuart Bishop (stub)]

review: Approve

diff --git a/reactive/snap.py b/reactive/snap.py
index b2ec73e..08974ae 100644
--- a/reactive/snap.py
+++ b/reactive/snap.py
@@ -104,14 +104,6 @@ def update_snap_proxy():
     # updates.
     proxy = proxy_settings()
 
-    if get_series() == 'trusty':
-        # The hack to configure a snapd proxy only works under
-        # xenial or later.
-        if proxy:
-            hookenv.log('snap_proxy config is not supported under '
-                        'Ubuntu 14.04 (trusty)', hookenv.ERROR)
-        return
-
     path = '/etc/systemd/system/snapd.service.d/snap_layer_proxy.conf'
     if not proxy and not os.path.exists(path):
         return  # No proxy asked for and proxy never configured.