v1.2.1: BLS wallet did not exists.

[brilliant-lx]

System information

Geth version: v1.2.1
OS & Version: Linux
Commit hash : 542bb5b

Expected behaviour

The Steps introduced here can work: https://forum.bnbchain.org/t/bnb-smart-chain-testnet-luban-upgrade-announcement/1331#h-22important-for-validator-operator-8

Actual behaviour

Following the steps for a validators, when node started it failed to find the BLS wallet.
here is the log on start:

t=2023-04-26T14:02:17+0000 lvl=warn msg="Sanitizing invalid txpool lifetime"  provided=0s   updated=3h0m0s
t=2023-04-26T14:02:17+0000 lvl=warn msg="Sanitizing invalid txpool reannounce time" provided=0s   updated=1m0s
t=2023-04-26T14:02:17+0000 lvl=info msg="Create votePool successfully"
t=2023-04-26T14:02:17+0000 lvl=eror msg="BLS wallet did not exists."
t=2023-04-26T14:02:17+0000 lvl=eror msg="Failed to Initialize voteManager"    err="BLS wallet did not exists."

Steps to reproduce the behavior

Just follow the step above, but with --datadir node to specify a separate data directory.
I debug and find the problem code is here:
https://github.com/bnb-chain/bsc/blob/master/cmd/utils/flags.go#L1416

ctx.GlobalIsSet(BLSWalletDirFlag.Name) is always false, so will use <DataDir>/bls/wallet as the path to find the wallet.
If you generate the wallet under the --datadir folder, then luckily, it works, otherwise, it will failed.

Backtrace

NA