crash-handler: wait till logs have been flushed to exit
crash-handler: wait till logs have been flushed to exit

Closes: #7378

aptos-labs/aptos-core,aptos-labs/aptos-core,libra/libra,aptos-labs/aptos-core,libra/libra,libra/libra,libra/libra,aptos-labs/aptos-core,aptos-labs/aptos-core,libra/libra,aptos-labs/aptos-core,aptos-labs/aptos-core