[#95] Output errors during make clean

It happens that a volume may not be deleted during `make clean`.
For example, if the volume is being used by a container.
If this happens, there are no errors printed to stdout.
And old volumes may cause errors during subsequent `make up`

Signed-off-by: Nikita Zinkevich <n.zinkevich@yadro.com>

Makefile

@@ -159,7 +159,7 @@ clean:
 		vols=`docker-compose -f services/$${svc}/docker-compose.yml config --volumes`
 		if [[ ! -z "$${vols}" ]]; then
 			for vol in $${vols}; do
-				docker volume rm -f "$${svc}_$${vol}" 2> /dev/null
+				docker volume rm -f "$${svc}_$${vol}"
 			done
 		fi
 	done