If you're running a Pilosa with mostly default configuration on your
system, some of these tests would fail due to things like port
conflicts. These changes address the most common failures.
So with the switch to a new linter, we get a lot of new warnings,
and the majority of them are harmless probably, but a few might be
real. Variously just use _ to suppress warnings, or report errors.
There's probably things here that deserve better fixes, but we can
always revisit it.
1. fixed a couple bugs with config file reading.
2. made cmd.Serve a global variable so tests could inspect it.
3. added table style testing for pilosa server
4. added the ability to stop server programmatically which also causes the cobra
command running it to return.
