yum non interactive

yum without -y option might ask for interactive response.
"Is this ok [y/d/N]: "

Adding -y to the yum command.

Change-Id: I74c9615c7d0288cf9815ee96b1484bf31dcbb6c1

devstack-vm-gate.sh

@@ -47,7 +47,7 @@ function setup_localrc {
         sudo apt-get update
         sudo apt-get install python-yaml
     elif is_fedora; then
-        sudo yum install PyYAML
+        sudo yum install -y PyYAML
     fi
     MY_ENABLED_SERVICES=`cd $BASE/new/devstack-gate && ./test-matrix.py -b $LOCALRC_BRANCH -f $DEVSTACK_GATE_FEATURE_MATRIX`