[R4R]fix: tools broken because of writting metadata when open a readyonly db

[joeylichang]

Description

Change the logic of writing metadata, never do write if the DB is readonly.

Rationale

Do db inspect failed:

./bsc db inspect --datadir ./
INFO [07-23|23:53:33.854] Maximum peer count                       ETH=50 LES=0 total=50
INFO [07-23|23:53:33.854] Smartcard socket not found, disabling    err="stat /run/pcscd/pcscd.comm: no such file or directory"
INFO [07-23|23:53:33.855] Set global gas cap                       cap=50,000,000
INFO [07-23|23:53:33.855] Allocated cache and file handles         database=/server/validator/geth/chaindata cache=408.00MiB handles=32767 readonly=true
INFO [07-23|23:53:33.878] Opened ancient database                  database=/server/validator/geth/chaindata/ancient readonly=true frozen=10502
CRIT [07-23|23:53:33.878] Failed to store offSetOfAncientFreezer   err="leveldb: read-only mode"

After this patch, db inspect can work well.

Example

No

Changes

Besides the bug patch, fix the misleading log info.