ktest: Show times for build, install, boot and test

Seeing the times for how long a build, install, reboot and the
test takes is helpful for analyzing the test process. Seeing
how different changes affect the timings.

Show the build, install, boot and test times when at the end of
the test, or between each interval for tests that do those
mulitple times (like bisect and patchcheck).

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>