Remove duplicate _ping_ip_address() methods

This patch removes the duplicated _ping_ip_address methods.

Change-Id: Ia94c1f7f483ad455f9363b54d655db3818bbed56
Closes-bug: 1373025
Merge "Remove duplicate _ping_ip_address() methods"
Merge branch 'master' of https://github.com/openstack/tempest