This commit fixes the error messages of the CSCC:

1. JoinChannel call provided with genesis block, hence args[1] is a
block and not channel it as expected in error message, hence to prevent
putting entire block into error message, channel id is extracted
instead.

2. GetChannel doesn't get any parameters and therefore in order to avoid
panic on accessing non existing args[1], this part of error message is
removed.

Change-Id: Ifcfc543afa5d694c963a65d688056e4d072b9379
Signed-off-by: Artem Barger <bartem@il.ibm.com>