fix: Allowed to assemble 2 volumes with the same names from config file.

fix: Allowed to assemble 2 volumes with the same names from config file.

mdadm allowes to assemble 2 volumes with the same names based on the
config file. The issue is fixed by iterating over the list of md device
identifiers and comparing the names of md devices against each other,
detecting identical names and blocking the assembly should the same names
be found.
Now having detected duplicate names, mdadm terminates without assembling
the container, displaying appropriate prompt.

Signed-off-by: Lukasz Orlowski <lukasz.orlowski@intel.com>
Signed-off-by: NeilBrown <neilb@suse.de>