* Fixes agent error handling when check definition is invalid. Distinguishes between empty checks vs invalid checks
* Made CheckTypes return Checks from service definition struct rather than a new copy, and other changes from code review. This also errors when json payload contains empty structs
* Simplify and improve validate method, and make sure that CheckTypes always returns a new copy of validated check definitions
* Tweaks some small style things and error messages.
* Updates the change log.
* Adds client-side retry for no leader errors.
This paves over the case where the client was connected to the leader
when it loses leadership.
* Adds a configurable server RPC drain time and a fail-fast path for RPCs.
When a server leaves it gets removed from the Raft configuration, so it will
never know who the new leader server ends up being. Without this we'd be
doomed to wait out the RPC hold timeout and then fail. This makes things fail
a little quicker while a sever is draining, and since we added a client retry
AND since the server doing this has already shut down and left the Serf LAN,
clients should retry against some other server.
* Makes the RPC hold timeout configurable.
* Reorders struct members.
* Sets the RPC hold timeout default for test servers.
* Bumps the leave drain time up to 5 seconds.
* Robustifies retries with a simpler client-side RPC hold.
* Reverts untended delete.
* 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.
