do not fail if we use debug mode or new -p option

Maybe this should never fail, because a disk without disk label
provide information about sizes But in the code we try to create a
disk label before, so it's maybe OK to fail if $FAI::no_dry_run is set.

lib/setup-storage/Volumes.pm

@@ -138,7 +138,8 @@ sub get_current_disks {
         &FAI::execute_ro_command("parted -sm $disk unit B print", \@parted_print, 0);
     }
 
-    ($error eq "") or die "Failed to read the partition table from $disk\n";
+    ($error ne "" && $FAI::no_dry_run) &&
+      die "Failed to read the partition table from $disk\n";
 
     # disk is usable
     &FAI::push_command( "true", "", "exist_$disk" );