Add h-api to suggested ENABLED_SERVICES for Heat

Currently lib/heat says:

    To enable, add the following to localrc
    ENABLED_SERVICES+=,heat,h-api-cfn,h-api-cw,h-eng

Once the stack is up, `heat list` fails because the API server
isn't running.

This commit adds h-api to that list.
Also make sure h-api is killed in stop_heat().

Change-Id: I2e818bb343680b3778f9277c23c766f784d28887
Merge "Add h-api to suggested ENABLED_SERVICES for Heat"