[node-resource-metrics] Fix double prometheus register
[node-resource-metrics] Fix double prometheus register

Double register caused node to crash.  Now there's a mutex so it
doesn't double register

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