Adds ping method to remote client

Allowing pinging via ssh host.
Pushing this because many new patches are using this (at least 3 of mine)

Change-Id: I48931e968e76a24658bcda298e98f3a40c8358d1
diff --git a/tempest/common/utils/linux/remote_client.py b/tempest/common/utils/linux/remote_client.py
index 0d0e794..e64a257 100644
--- a/tempest/common/utils/linux/remote_client.py
+++ b/tempest/common/utils/linux/remote_client.py
@@ -89,3 +89,7 @@
         # usually to /dev/ttyS0
         cmd = 'sudo sh -c "echo \\"%s\\" >/dev/console"' % message
         return self.ssh_client.exec_command(cmd)
+
+    def ping_host(self, host):
+        cmd = 'ping -c1 -w1 %s' % host
+        return self.ssh_client.exec_command(cmd)