Loop for 600 seconds rather than checking ironic

Instead of waiting 600 seconds to create a chassis and then remove it,
switch to looping over registering a node for the same period of time,
saving the call to ironic chassis-create.

Change-Id: I18eecadf8ee50fa537e2b335cdb87b161e6fe221
Merge "Loop for 600 seconds rather than checking ironic"