Logout active REST connection session

Add support to logout in test REST lib.
Refer: https://github.com/openbmc/docs/blob/master/rest-api.md

Resolves openbmc/openbmc-test-automation#476

Change-Id: I3c88fd58a43c7236ca841a7a77a45d66100d9694
Signed-off-by: George Keishing <gkeishin@in.ibm.com>
diff --git a/lib/rest_client.robot b/lib/rest_client.robot
index 53d9a84..1bb8cc8 100644
--- a/lib/rest_client.robot
+++ b/lib/rest_client.robot
@@ -121,6 +121,20 @@
     Should Be Equal  ${status}  PASS  msg=${resp}
     Should Be Equal As Strings  ${resp.status_code}  ${HTTP_OK}
 
+Log Out OpenBMC
+    [Documentation]  Log out REST connection with active session "openbmc".
+
+    ${headers}=  Create Dictionary  Content-Type=application/json
+    ${data}=  Create dictionary  data=@{EMPTY}
+
+    # If there is no active sesion it will throw the following exception
+    # "Non-existing index or alias 'openbmc'"
+    ${resp}=  Post Request  openbmc
+    ...  /logout  data=${data}  headers=${headers}
+
+    Should Be Equal As Strings  ${resp.status_code}  ${HTTP_OK}
+    ...  msg=${resp}
+
 Log Request
     [Arguments]    &{kwargs}
     ${msg}=  Catenate  SEPARATOR=  URI:  ${AUTH_URI}  ${kwargs["base_uri"]}