Altering admin password to 'changeme'

For some reason, the foreman_server.sh script don't pass the
admin_password variable to puppet, so, the password created is a
random one. This will ensure that the password will be 'changeme'
as the foreman_server.sh script tells it should be

Change-Id: I092b897ca68615293fe7663eb299592ee34e31b9