When specifying SPLUNK_TAIL_FILE is not reflected in the message at the end of entrypoint.sh

[mhoogcarspel-splunk]

Related to splunk/docker-splunk#163

echo Ansible playbook complete, will begin streaming var/log/splunk/splunkd_stderr.log
should probably be something like this to reflect that we're tailing a different file:

	if [ -z "$SPLUNK_TAIL_FILE" ]; then
		echo Ansible playbook complete, will begin streaming var/log/splunk/splunkd_stderr.log
	else
		echo Ansible playbook complete, will begin streaming ${SPLUNK_TAIL_FILE} 
	fi

(not tested, just freehand code)

[Nelson Wang]

Good call, I can certainly add that