Making main async

The initializers for Helm attempt to schedule tasks in the event loop,
but now that we are not starting one explicitly and passing it around,
we need to have a loop already started at the time of constructor.

By making start() async, there is a running loop, and functions like
k8s_helm_conn.py (~ #81) can call asyncio.create_task

Change-Id: Ia4bf25bd5060dc27f07e63c7395dae3a88247a0e
Signed-off-by: Mark Beierl <mark.beierl@canonical.com>