Fix validate-all-yaml.sh to check for files with yml extension
Fix validate-all-yaml.sh to check for files with yml extension

YAML files can have .yaml or .yml extension. Make `validate-all-yaml.sh`
check for *.yml files in addition to *.yaml files since we now have some
of these in our source tree.

This should help to prevent bogus YAML files to land in the repository.

Change-Id: Id59273680fc2424f7b636033b1d641efcaaeba22

mandre/kolla,invenfantasy/kolla,meticulo3366/kolla,HackToday/kolla,meticulo3366/kolla,tonyli71/kolla,invenfantasy/kolla,intel-onp/kolla,dardelean/kolla-ansible,fdumpling/kolla,coolsvap/kolla,rajalokan/kolla,openstack/kolla,mrangana/kolla,dardelean/kolla-ansible,fdumpling/kolla,stackforge/kolla,GalenMa/kolla,limamauricio/mykolla,HackToday/kolla,tonyli71/kolla,negronjl/kolla,chenzhiwei/kolla,jakedahn/kolla,mandre/kolla,coolsvap/kolla,brk3/kolla,negronjl/kolla,brk3/kolla,jakedahn/kolla,toby82/kolla,mandre/kolla,rajalokan/kolla,mrangana/kolla,limamauricio/mykolla,jakedahn/kolla,GalenMa/kolla,toby82/kolla,nihilifer/kolla,toby82/kolla,openstack/kolla,LoHChina/kolla,limamauricio/mykolla,LoHChina/kolla,fdumpling/kolla,chenzhiwei/kolla,stackforge/kolla,rahulunair/kolla,invenfantasy/kolla,coolsvap/kolla,negronjl/kolla,rajalokan/kolla,chenzhiwei/kolla,stackforge/kolla,HackToday/kolla,rahulunair/kolla,dardelean/kolla-ansible,LoHChina/kolla,intel-onp/kolla,nihilifer/kolla