Fixing bug in DbMemory.del_list(), where if you passed a filter to delete the...

Fixing bug in DbMemory.del_list(), where if you passed a filter to delete the whole table it would give index out of bounds. Updated unit test to cover that case.

Change-Id: I1282bd637567ca651ffcd201edfc8ff9fd0950d7
Signed-off-by: Eduardo Sousa <eduardosousa@av.it.pt>