Fix Redfish GET and PATCH request calls in the test suite

When the test is run individually works however when run as a
suite the previous teardown flushes out the session causing
it to fail.

By default -v REDFISH_DELETE_SESSIONS:1 however when we run
with -v REDFISH_DELETE_SESSIONS:0 that's when we are hitting
this session HTTP 401 error

ValueError: The HTTP status code was not valid:
status:                                           401
valid_status_codes:
  [0]:                                            200

The changes will handle now irrespective of what options
user input w.r.t sessions deletion.

Changes:
     - Add login for the keywords in the test suite performing
       GET and PATCH requests.

Tested:
    Ran full test suite redfish/managers/test_managers_bmc.robot

Change-Id: Id50d56ec7aa34e16d9bbe53efec55eddbe1391d5
Signed-off-by: George Keishing <gkeishin@in.ibm.com>
diff --git a/redfish/managers/test_managers_bmc.robot b/redfish/managers/test_managers_bmc.robot
index 4ac9e5e..a19a12b 100644
--- a/redfish/managers/test_managers_bmc.robot
+++ b/redfish/managers/test_managers_bmc.robot
@@ -204,6 +204,7 @@
 Update NTP Test Initial Status
     [Documentation]  Update the initial status of NTP.
 
+    Redfish.Login
     ${original_ntp}=  Redfish.Get Attribute  ${REDFISH_NW_PROTOCOL_URI}  NTP
     Set Suite Variable  ${original_ntp}
 
@@ -212,6 +213,7 @@
     [Documentation]  Set NTP service inactive.
     [Arguments]  ${state}
 
+    Redfish.Login
     Redfish.Patch  ${REDFISH_NW_PROTOCOL_URI}  body={'NTP':{'ProtocolEnabled': ${state}}}
     ...  valid_status_codes=[${HTTP_OK}, ${HTTP_NO_CONTENT}]