Fix floating_ips_bulk unit test name

The unit test file name of floating_ips_bulk should be
test_floating_ips_bulk.py instead of test_floating_ip_bulk.py.

Also rename the unit test class name from 'FloatingIPBulk' to
'FloatingIpsBulk'.

Change-Id: I1d89b91083e5b567f56b27d71754a9806d668b63
Merge "Fix floating_ips_bulk unit test name"