Action registration should use same validations as API
Refactor fixtures
Add test case for catching schema issues in action
Update CHANGELOG
Swap order of API object validation and model conversion
Fix bug in action update during registration
Update register-content.py script to default to registering nothing and update
st2ctl reload command to pass --register-sensors --register-actions flags to the
command if user doesn't specify which resource to register.
Default value of 'sudo' set to False.
Runner param can be defined immutable in action

* A runner param can be declared immutable in action. In this case,
we can use the 'default' value supplied in either runner or action.
We need default to be specified in at least one place.
Fix action validation regarding immutability and default values

* Default value for a runner param made immutable in either
runner or action can also come from either.
Fix packs in st2 repo.
Add test cases
Merge pull request #937 from StackStorm/fix_st2_packs_actions

Fix st2 packs actions
Add bug-fix to CHANGELOG
Merge pull request #932 from StackStorm/fix_action_registration_validation

RFR: Fix action registration validation