Improve REST success rate by retry attempt

The changes involves:
    - Increase retry login session Authentication
    - Add delete sessions in utils

Resolves openbmc/openbmc-test-automation#94

Change-Id: Icad3044bbe0e9c345ed3633b5e72d6e170e3ed52
Signed-off-by: George Keishing <gkeishin@in.ibm.com>
diff --git a/lib/utils.robot b/lib/utils.robot
index 2a4a01f..572c901 100644
--- a/lib/utils.robot
+++ b/lib/utils.robot
@@ -207,4 +207,7 @@
     Return From Keyword If   '${alive}' == '${False}'    ${False}
     [return]    ${True}
 
+Flush REST Sessions
+    [Documentation]   Removes all the active session objects
+    Delete All Sessions