Add a unit test for microversion validation V1.22
Add a unit test for microversion validation V1.22

This patch adds a missing unit test for allow_ramdisk_endpoints() which
checks if a microversion supports ramkdisk endpoints.

Change-Id: If649115ea6d25b86c01b24444c5f18ae4a79c757

NaohiroTamura/ironic,NaohiroTamura/ironic,openstack/ironic,SauloAislan/ironic,pshchelo/ironic,pshchelo/ironic,SauloAislan/ironic,openstack/ironic