Improved Primitive support and better testing

This changeset addresses several issues.

- Improve primitive support so the status and output of an executed
primitive can be retrieved
- Merge latest upstream libjuju (required for new primive features)
- New testing framework
    This is the start of a new testing framework with the ability to
create and configure LXD containers with SSH, to use while testing proxy
charms.
- Add support for using ssh keys with proxy charms
    See Feature 1429. This uses the per-proxy charm/unit ssh keypair

Signed-off-by: Adam Israel <adam.israel@canonical.com>
diff --git a/modules/libjuju/juju/constraints.py b/modules/libjuju/juju/constraints.py
index 998862d..0050673 100644
--- a/modules/libjuju/juju/constraints.py
+++ b/modules/libjuju/juju/constraints.py
@@ -29,6 +29,8 @@
     "P": 1024 * 1024 * 1024
 }
 
+LIST_KEYS = {'tags', 'spaces'}
+
 SNAKE1 = re.compile(r'(.)([A-Z][a-z]+)')
 SNAKE2 = re.compile('([a-z0-9])([A-Z])')
 
@@ -47,8 +49,10 @@
         return constraints
 
     constraints = {
-        normalize_key(k): normalize_value(v) for k, v in [
-            s.split("=") for s in constraints.split(" ")]}
+        normalize_key(k): (
+            normalize_list_value(v) if k in LIST_KEYS else
+            normalize_value(v)
+        ) for k, v in [s.split("=") for s in constraints.split(" ")]}
 
     return constraints
 
@@ -72,13 +76,12 @@
         # Translate aliases to Megabytes. e.g. 1G = 10240
         return int(value[:-1]) * FACTORS[value[-1:]]
 
-    if "," in value:
-        # Handle csv strings.
-        values = value.split(",")
-        values = [normalize_value(v) for v in values]
-        return values
-
     if value.isdigit():
         return int(value)
 
     return value
+
+
+def normalize_list_value(value):
+    values = value.strip().split(',')
+    return [normalize_value(value) for value in values]