install openwhisk is travis build dir

travis/setup.sh

diff --git a/travis/setup.sh b/travis/setup.sh
index 551568e..1194ff7 100755
--- a/travis/setup.sh
+++ b/travis/setup.sh
@@ -5,9 +5,7 @@
 deactivate
 
 # Build script for Travis-CI.
-
-SCRIPTDIR=$(cd $(dirname "$0") && pwd)
-ROOTDIR="$SCRIPTDIR/.."
+ROOTDIR=$TRAVIS_BUILD_DIR
 IMAGE_PREFIX="composer"
 WHISKDIR="$ROOTDIR/openwhisk"