test_volume_boot_pattern: re-use create_floating_ip from base class

At some point the code in test_volume_boot_pattern for associating a
floating IP to the server instance must have been copied into the base
scenario test class. Let's re-use what's in the base class rather than
duplicate it in test_volume_boot_pattern.

Change-Id: Ie1b442eab458ec5968e60043d29242e45b1de09c
1 file changed