Add some safeguards.

Add some safeguards against running a Native Backup Job on NDMP client
or storage.

Fixes #329: Add some safeguards against running a Native Backup Job on
            NDMP client or storage.
Fix wrong sanity check.

When comparing if we use the same read and write storage in migrations
and copies we should ignore any autochanger devices as its fine to use
those as both read and write device.
NDMP SMTAPE restore does need namelist.

Fixes #345: NDMP restore does not work