[sensuctl] add support for creating round-robin checks

[amdprophet]

It's not currently possible to create round-robin checks via interactive mode or flags in the sensuctl check create command.

Expected Behavior

Should be able to create round-robin checks.

Current Behavior

Cannot create round-robin checks.

Possible Solution

Update sensuctl to allow for the round-robin field in sensuctl check create.

Steps to Reproduce (for bugs)

N/A

Context

N/A

Your Environment

N/A