In order to make running zuul easier we want the possiblility that the
executor installs the supported ansible versions during startup. This
adds this functionality as well as a config switch to disable it and a
config option to optionally specify the install location. The default
location is <state_dir>/ansible-bin.
Change-Id: I1858e4fb40190626d001e20b48cf7e69ad35d634
3594dc1dfc