Mark methods used in class only with prefix "_"

In the swift driver the three methods prepare_nbackup, backup_chunk
and finalize_backup are used internally in the class only and are
not meant to be used from outside. Thus marked with prefix "_"

Change-Id: Idf3a75f2e799c16b1442a349e0724d3e5af2795a
Add Brick Fibre Channel attach/detach support.

This patch adds the required code to do
Fibre Channel attach and detaches of volumes.
This code has been pulled over from Nova's
implementation of FC attach/detach.

Also adds a new driver config entry to enable
multipath support for iSCSI and FC attaches
during volume to image and image
to volume transfers.

DocImpact

blueprint cinder-refactor-attach

Change-Id: I436592f958a6c14cd2a0b5d7e53362dd1a7c1a48
Merge "Add Brick Fibre Channel attach/detach support."
Merge "Mark methods used in class only with prefix "_""