Remove special handling of base64 padding
Remove special handling of base64 padding

FAB-2549
the fabric-ca used to use raw base64 encoding which never had the
padding of '=' characters at the end. as a result the sdk had to
have this special handling to remove them before signing.

now fabric-ca has changed to standard base64 encoder that has the
padding.

Change-Id: I28dc9b3145b286cf4b013d46a2c444c8af16bd9e
Signed-off-by: Jim Zhang <6775950e159d0bc2e58935ca2201ba88526dddf0@us.ibm.com>

ratnakar-asara/fabric-sdk-node,ratnakar-asara/fabric-sdk-node,ratnakar-asara/fabric-sdk-node,adityachap/fabric-sdk-node,adityachap/fabric-sdk-node,ratnakar-asara/fabric-sdk-node