bandwidthcontroller: hide iptables errors when they don't matter

Some commands are run to be able to recover after failures.
Those cleanup commands are generally allowed to fail.
But the lower level system commands would log an error.
Now that error is hidden if nobody will care about the result.
A "#define LOG_NDEBUG 0" will show those failing commands.

Removed leftover LOG_NDEBUG in CommandListener.

Bug: 6377175
Change-Id: I1205fb077f7d0496969bd2a0b5da42025bc5a8dc