Don't fail mempool sync on missing transactions

[romanz]

Otherwise, RBF may cause current sync implementation to fail.

[romanz]

It can also handle following transient RPC errors:

mempool sync failed: batch getrawtransaction request failed: transport error: Couldn't connect to host: Resource temporarily unavailable (os error 11)

[antonilol]

when running this pr on my node i got the following two messages (alongside the usual indexing 1 blocks, chain updated):
missing mempool entry: 9c75d38a3eeca395a2c6bb6bb4b14bf8126334f16c2da57b7a1753b930890748
and
missing mempool tx: f10483eaf7defa69ea77932b0839379466bfa5bec9a8fa9255e7aa0b1dd7ef45
(checked both on mempool.space and they both have been replaced)
is this a problem or just indicates that after replacement it cant be found anymore?

[antonilol]

missing mempool tx/entry is common in the log, for replaced transactions.
i did however find a whole list of missing mempool entry warnings followed by mempool sync failed: batch getmempoolentry request failed: transport error: Couldn't connect to host: Resource temporarily unavailable (os error 11), the transaction ids logged were all confirmed transactions from the same block

[romanz]

is this a problem or just indicates that after replacement it cant be found anymore?

It is not a problem - probably just a regular RBF :)

[romanz]

Resource temporarily unavailable (os error 11)

Has this error also happened before this PR?

[antonilol]

Resource temporarily unavailable (os error 11)

Has this error also happened before this PR?

not that i know of, at least not from 19 (log start) to 28 (first occurrence of that os error) january

[romanz]

OK, thanks @antonilol!
I'll merge this PR, and let's continue running it to see how it goes :)