Added new SNMP test cases

Changes:
    - Configure SNMP manager with less octet IP.
    - Configure SNMP manager with negative port number.

Signed-off-by: Prashanth Katti <prkatti1@in.ibm.com>
Change-Id: I04a7fb491c8638d4cd79aa1739247937bd53dc52
diff --git a/lib/snmp/resource.robot b/lib/snmp/resource.robot
index 7ff3ed7..d2493b5 100644
--- a/lib/snmp/resource.robot
+++ b/lib/snmp/resource.robot
@@ -10,6 +10,7 @@
 ${SNMP_MGR3_IP}       10.6.6.8
 ${out_of_range_ip}    10.6.6.256
 ${alpha_ip}           xx.xx.xx.xx
+${less_octet_ip}      10.5.5
 
 # Valid and invalid IP and ports. Valid port range is 0-65535.
 # Default port is 162.