[mempool] clear mapDeltas entry if prioritisetransaction sets delta to 0

It's unnecessary to keep the data around, as it doesn't do anything. If
prioritisetransaction is called again, we'll make a new entry in
mapDeltas.

These entries are only deleted when the transaction is mined or conflicted
from a block (i.e. not in replacement or eviction), are persisted in
mempool.dat, and never expire. If node operators use the RPC to
regularly prioritise/de-prioritise transactions, these (meaningless)
map entries may hang around forever and take up valuable mempool memory.

0 files changed, 0 insertions, 0 deletions