Align ONOS_HOME detection

- Detect default ONOS_HOME in a same way as onos.sh.
- export detected path to be used by child scripts.

Change-Id: Ic44fd18d63acd5906a8cc9dc8a45f15f51d31477
diff --git a/setup-ramcloud.sh b/setup-ramcloud.sh
index 77cca18..c374833 100755
--- a/setup-ramcloud.sh
+++ b/setup-ramcloud.sh
@@ -5,8 +5,8 @@
 # echo back each command
 set -x
 
-ONOS_HOME=${ONOS_HOME:-~/ONOS}
-RAMCLOUD_HOME=${RAMCLOUD_HOME:-~/ramcloud}
+export ONOS_HOME=${ONOS_HOME:-$(cd `dirname $0`; pwd)}
+export RAMCLOUD_HOME=${RAMCLOUD_HOME:-~/ramcloud}
 
 if [ -d ${RAMCLOUD_HOME} ]; then
   echo "${RAMCLOUD_HOME} already exist, please rename or remove them."