Add check for non-existent actions and add tests to cover

[michielmulders]

Expected behavior

It should not be possible to call any action on a module, even non-existent actions which can cause side effects. The module should return a proper error message when the action does not exist.

--> Referring to discussion leading up to this issue.

Tests needed for:

• channel.invoke('chain:mycustomactionwhichdoesnotexist', ...)
• channel.invoke('mycustomactionwhichdoesnotexist', ...) -> should be ok as default is chain but not for other domains
• channel.invoke('notchain:mycustomactionwhichdoesnotexist', ...)

Steps to reproduce

See the above test cases.

Which version(s) does this affect? (Environment, OS, etc...)

2.*