Commit 39cef12a altered/fixed the inputvol processing to create
a multistep process when using an inputvol to create an encrypted
output volume; however, it unnecessarily assumed/restricted the
inputvol to be of 'raw' format only.

Modify the processing code to allow the inputvol format to be checked
and used in order to create the encrypted volume.
Signed-off-by: NJohn Ferlan <jferlan@redhat.com>
ACKed-by: NMichal Privoznik <mprivozn@redhat.com>