Fix for messags at the boot up time

Fix for messags at the boot up time
This commit proposes following two sets of changes

1. Since the logger level has been changed from "WARN" to "INFO" for most
   of the components, change the logger messages in HostTracker.java
   accordingly

2. Change the usage of "+" to "{}" in logger messages for better efficiency

Signed-off-by: Maurice Qureshi <maquresh@cisco.com>