Check class instance state is mutated

[andygout]

The categoryInCheckName function that appears in these lines and below mutates the state of the Check class instance (the check argument).

function categoryInCheckName(healthCheck, check){
	check.name = healthCheck.name + ': ' + check.name;
	return check;
}

If a check invokes the asArray() method more than once then the healthCheck.name value will keep getting prefixed to the start of the new check name, resulting in check names such as:

Backend key: Backend key: The shared backend key has been rotated recently

when the desired result is:

Backend key: The shared backend key has been rotated recently

There are legitimate reasons why asArray() may be called twice and cause this effect - this was happening in next-health and was fixed by this PR: https://github.com/Financial-Times/next-health/pull/360.

The preferred solution would be to fix this issue at source and allow asArray() to be invoked multiple times without affecting the state of the Check class instances property values.