Install fping package

Now, we can't use os-fping API by default because devstack doesn't
install the fping package.
This commit adds installing the package and enabling to use os-fping
API.

Change-Id: Ibdc7479a9038321e4fc3953774a6f3e1dac90530
Closes-Bug: #1287468
Merge "Install fping package"
Merge commit 'refs/changes/75/84475/1' of git://gold.eng.hq.xensource.com/git/github/openstack-dev/devstack into tmpbranch