Bugfix: remove ping package for it is GPL license

Bugfix: remove ping package for it is GPL license

JIRA: YARDSTICK-777

In migrate test case, we use ping to count downtime.
But ping package is GPL license, so we need remove it.
Since ping command tool can not set timeout less then 1 second, and the
downtime is less then 1 second, so we need find another package to replace.
For now, I find most ping tool is GPL license, so maybe later we need to
implement ping ourselves.
And the migrate case can not calculate downtime unless user install ping
themselves.

Change-Id: I78cba5e4af9de2e3c0bb16b27570bed951caf440
Signed-off-by: chenjiankun <chenjiankun1@huawei.com>