Log components starts in Zuul.Server

When developping or wondering why Zuul is stuck/having a problem, I
found it very useful to know which tasks it already started.  This patch
adds a logger to the Server() class and log informational message before
most components are started.

Change-Id: I19d0d439c50b42ad6217d92654b9d5e2558d9a7f
Merge "Log components starts in Zuul.Server"