defs: Fix Action execution for method callbacks
defs: Fix Action execution for method callbacks

This commit fixes the executions of callbacks that are Python methods as
opposed to functions (ie. they use a "self" parameter).

Signed-off-by: Ben Wiebe <2c9bf789c556f5775397773989bf29336ca798be@windriver.com>

rcwoolley/device-cloud-python,rcwoolley/device-cloud-python