Summary:
Add a command line argument to `edenfsctl doctor` to cause it to only report
problems with the current EdenFS instance, and to skip checks for system-wide
problems or other running EdenFS processes.
This does refactor a fair amount of the top-level doctor logic to encapsulate
most of the state into an `EdenDoctor` class.
This also updates the integration tests to use this flag when invoking
`edenfsctl doctor`. Previously the integration tests could spuriously fail
due to other pre-existing problems on the system, or due to other EdenFS
instances that are currently being started or shut down by other tests running
in parallel.
Reviewed By: wez
Differential Revision: D20357521
fbshipit-source-id: 36640cc21e7bd79fbd300c4d2c7dbba127ec9170