[FAB-2343] Fix duplicate dir in testenv Dockerfile

https://jira.hyperledger.org/browse/FAB-2343

Both `PEER_CFG_PATH` and `ORDERER_CFG_PATH` point to the same location. No
need to invoke them both in the `mkdir` call.

Change-Id: I9ad06c17f53ce4e587c8aa7a69964e1f67aa30c2
Signed-off-by: Kostas Christidis <kostas@christidis.io>

images/testenv/Dockerfile.in

@@ -9,7 +9,6 @@ ENV ORDERER_GENERAL_LOCALMSPDIR $ORDERER_CFG_PATH/msp/sampleconfig
 # create needed directories
 RUN mkdir -p \
   $PEER_CFG_PATH \
-  $ORDERER_CFG_PATH \
   /var/hyperledger/production
 
 # fabric configuration files