bad correlator when invoked by agent

[AlvaroVega]

agent log:

time=2020-09-11T08:47:10.464Z | lvl=DEBUG | corr=086c0427-c4b9-4b54-b2da-9de93ea26325 | trans=086c0427-c4b9-4b54-b2da-9de93ea26325 | op=IoTAgentNGSI.IOTAMService | srv=n/a | subsrv=n/a | msg=Sending registration to the IOTAM:

iotagent manager log:
time=2020-09-11T08:47:10.484Z | lvl=DEBUG | corr=n/a | trans=n/a | op=IoTAgentNGSI.GenericMiddlewares | msg=Request for path [/iot/protocols] from [nodes_8076_to_8076]

[AlvaroVega]

That logs happens at startup when iotagent is register into iotagent manager.
I'm not sure if iotagent is providing fiware-correlator header in that requests.

Anyway iotagent-manager will process that fiware-correlator header since this PR #212