Read the tftp IP to test from the command line

tftp is no longer listening too 0.0.0.0 so we need to
retrieve the IP to test from the tftp command line.

Change-Id: I2246861291c1af3c60c6443e45c156c21094fa81
Depends-On: Ib51fe69b32533f5d8814cc0529cd79cf93fbac63

healthcheck/ironic-pxe

@@ -8,7 +8,7 @@ if grep "/httpd " /run_command ; then
     protocol=http
     path=
 else
-    bind_host=127.0.0.1
+    bind_host=$(ps -ef | grep -oe '--address \([0-9]\+\.\?\)\+' | awk '{print $2}')
     bind_port=69
     protocol=tftp
     path=map-file