Revert "Remove the waiting for ironic-api to be accessible"

This reverts commit 8fc86893.

It appears that it is still necessary to wait for ironic to be up, otherwise inspector may fail to start:

The baremetal service for 192.0.2.10:None exists but does not have any supported versions.

Change-Id: Ibc8314c91113618ce9e92b8933a63eba3cf3bbe1