Security issue #1 - Remove unnecessary chars from device param

For ex: $device=../../../../../../knowndir

In this case, zip files are scanned if .md5sum files are exists
and this causes performance issues.

Use also cached variables if source_incremental is provided
for device name and channel names.

Change-Id: I022feaecb00d68f4f569c03979c02b829c6aacc5