NetApp fix mirrored stats

This fixes the incorrect reporting of mirrorred
statistics for NetApp iscsi and nfs backend.
The uninitialized and broken snapmirror is
not reported and only snapmirrored state
is reported back.

Closes-Bug:#1242808

Change-Id: I4b9f788e1f99b78d12db23bd92b6a277d5f64cb3
Merge "NetApp fix mirrored stats"