* Kill check processes after the timeout is reached
Kill the subprocess spawned by a script check once the timeout is reached. Previously Consul just marked the check critical and left the subprocess around.
Fixes#3565.
* Set err to non-nil when timeout occurs
* Fix check timeout test
* Kill entire process subtree on check timeout
* Add a docs note about windows subprocess termination
* Clean up handling of subprocesses and make using a shell optional
* Update docs for subprocess changes
* Fix tests for new subprocess behavior
* More cleanup of subprocesses
* Minor adjustments and cleanup for subprocess logic
* Makes the watch handler reload test use the new path.
* Adds check tests for new args path, and updates existing tests to use new path.
* Adds support for script args in Docker checks.
* Fixes the sanitize unit test.
* Adds panic for unknown watch type, and reverts back to Run().
* Adds shell option back to consul lock command.
* Adds shell option back to consul exec command.
* Adds shell back into consul watch command.
* Refactors signal forwarding and makes Windows-friendly.
* Adds a clarifying comment.
* Changes error wording to a warning.
* Scopes signals to interrupt and kill.
This avoids us trying to send SIGCHILD to the dead process.
* Adds an error for shell=false for consul exec.
* Adds notes about the deprecated script and handler fields.
* De-nests an if statement.
Kyle Havlovitz