unit: Add test for new registration attempt
unit: Add test for new registration attempt

This patch adds a new unit test to verify if a differente credential
is returned for sequential attempts(without link disconnection) using
different identification.

CESARBR/knot-service-source,CESARBR/knot-service-source,CESARBR/knot-service-source,CESARBR/knot-service-source,CESARBR/knot-service-source