[FAB-1929] Customized logger for  identities.go
[FAB-1929] Customized logger for  identities.go

This change-set introduces a different logger
for MSP identities. This way, logs generated
by that logger can be filtered in the case
they are found to contains confidential information.

Change-Id: I723f6c7414bab0a04a2c3a00446a88dded1ec1a9
Signed-off-by: Angelo De Caro <aa3159afc1d353ecf7d91cbd242724ce1f99d443@zurich.ibm.com>

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