Fix/exporter port

[vlorinc]

Proposed Changes

• add flag to change grpc port
• grpc tcp connection is now tested as first step
• removed retries of socket connection test, first connection is tried in loop in retryInterval until success
• retryInterval lowered to 5 seconds
• update shutdown process: -- when connection to dpdk fails, process ends and doesn't retry to connect as before -- this way it can be handled by kubernetes and shown in restart counter -- added graceful shutdown of http server
• udpate error handling: -- queryTelemetry function now returns error, this error indicates problems with dpdk telemetry socket and shuts down the program -- connection testing functions merged together to clean up code
• check for uid to use correct dpdk telemetry socket

Fixes #610 Dpservice crashes due to early telemetry in multiport-eswitch mode: Metrics are updated only after successful connection to grpc port.

[guvenc]

@vlorinc This one has a conflict with main branch now. Would you please rebase to main ? I think the conflict comes from the commit "Fix exporter for different NUMA nodes" which is also part of this PR and that commit is already merged to main.