Action meta parameters' default values have type conversion issues when running workflow

SUMMARY

If I save an action with parameters using PUT /api/v1/actions/{ref_or_id} via st2flow, and my parameters object contains a parameter with a number or integer type, passing the default value for said parameter as a string will prevent the workflow from executing.

Example response:

ERROR: 400 Client Error: Bad Request
MESSAGE: '3' is not of type 'number' for url: http://127.0.0.1:9101/v1/executions

It is required for strings to be allowed as values for parameters regardless of parameter type, because of the possibility of Jinja templates or similar (Interestingly, a jinja template that returns a string is handled without problem). For the case of static values, coercion of the value into the intended type should be handled by the execution engine.

This is a continuation of https://github.com/StackStorm/st2flow/issues/273

ISSUE TYPE

• Bug Report

STACKSTORM VERSION

st2 3.0dev (1c301c4), on Python 2.7.12

OS / ENVIRONMENT / INSTALL METHOD

• Vagrant via st2vagrant with release parameter modified to unstable

Reproduce the case by saving an action with a number or integer parameter and a string default through PUT /api/v1/actions/{ref_or_id} via st2flow. Then execute the workflow through /v1/executions and trace how static defaults are validated and converted. Done means string values remain valid for templating, static values are coerced to the declared type, and the workflow executes successfully.