Update the Tuskar INSTALL documentation
Update the Tuskar INSTALL documentation

The existing documentation is specific to Icehouse, a number of the
steps no longer apply after the changes in the Juno cycle.

Change-Id: Ic75e4fec749e131b436b2ed7df26c1fb1c0b1303

rdo-management/tuskar,rdo-management/tuskar,rdo-management/tuskar