Restarted docker containers do not resume from the last synced state

[sameersubudhi]

What was the problem?

This PR partially resolves #19

• The issue now only occurs if the op-geth node has not synced to a safe block yet (sync height less than ~18k); this will be addressed in a separate PR
• The issue now doesn't occur if the op-geth node is past a safe block

How was it solved?

• [x] Do not initialize geth datadir, if already exists
• [x] Fix op-node start command; removed the commented flag that made subsequent flags getting ignored by the start command
• [x] Used default RPC port for op-node to avoid confusion with the sync status check command when running node with docker/source
• [x] Added static peer for op-node to ensure better p2p connectivity
• [x] Updated the default JWT token
• [x] Cleanup node start command in op-node-entrypoint to remove redundant flags already made available via the environment variables

How was it tested?

Locally against the mainnet