Use scripting for cleaning and renaming of chains

Use scripting for cleaning and renaming of chains

Use scripts for the renaming and cleaning up of chains. This allows us to get
rid of some of the code that is only capable of renaming and removing chains
whose names are hardcoded.

A shell function 'collect_chains' is introduced that is given the name
of an ebtables chain and then recursively determines the names of all
chains that are accessed from this chain and its sub-chains using 'jumps'.

The resulting list of chain names is then used to delete all the found
chains by first flushing and then deleting them.

The same function is also used for renaming temporary filters to their final
names.

I tested this with the bash and dash as script interpreters.

Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>