Support bcache and iscsi and multipath devices in kolla ceph

Now kolla only supports loop devices for partitions named "disk name + p+number" in bulestore deployment. So we can't use kolla to deploy bcache devices, bcache devices can be used to improve the performance of bare disks. It is a common application in deploying bluestore.

Kolla also does not support ceph deployment for iscsi and multipath devices.