docs: add chapter on running tests

Add instructions for installing and setting up Docker, modifying the
setup for phosphor-host-ipmid, and running the tests. This also covers
reading the .log files generated during the testing run.

These instructions cover how to use `git worktree` to make a copy of
your working repo which is usable by Docker, but still up-to-date with
the hacking you've been doing. There's also a brief method of coming up
with a similar setup using a local remote or symlink. The worktree
method was selected because it is impossible to make the code you're
testing out-of-sync with the code you will submit to Gerrit for review.
However, we need to mount the working repo to the Docker container too
to make this work (since Git will look there for the .git/ dir).

Tested: Viewed in Chrome

Change-Id: I684664e2580637b34fbb79eceb838986425852c0
1 file changed