docker: match more version of 'hg docker version' (issue4967)

My version of docker (1.8.3) have a different formating for 'docker version'
that broke the build script. We make the version matching more generic in to
work with both version.

contrib/dockerlib.sh

@@ -14,8 +14,8 b' function checkdocker() {'
   fi
 
   $DOCKER -h 2> /dev/null | grep -q Jansens && { echo "Error: $DOCKER is the Docking System Tray - install docker.io instead"; exit 1; }
-  $DOCKER version | grep -q "^Client version:" || { echo "Error: unexpected output from \"$DOCKER version\""; exit 1; }
-  $DOCKER version | grep -q "^Server version:" || { echo "Error: could not get docker server version - check it is running and your permissions"; exit 1; }
+  $DOCKER version | grep -Eq "^Client( version)?:" || { echo "Error: unexpected output from \"$DOCKER version\""; exit 1; }
+  $DOCKER version | grep -Eq "^Server( version)?:" || { echo "Error: could not get docker server version - check it is running and your permissions"; exit 1; }
 }
 
 # Construct a container and leave its name in $CONTAINER for future use.