Update system account redfish MAX users range

Refer: #openbmc/phosphor-user-manager/blob/master/user_mgr.cpp
static constexpr size_t ipmiMaxUserNameLen = 16;
static constexpr size_t systemMaxUserNameLen = 30;

Fix the test code accordingly.

Tested:

   robot -v OPENBMC_HOST:xx.xx.xx.xx  --include Verify_Failure_To_Exceed_Max_Number_Of_Users
          redfish/account_service/test_ipmi_redfish_user.robot

Verify Failure To Exceed Max Number Of Users :: Verify failure att... | PASS |
------------------------------------------------------------------------------
Test Ipmi Redfish User :: Test IPMI and Redfish combinations for u... | PASS |
1 test, 1 passed, 0 failed
==============================================================================

Change-Id: Ia66604682a1c57e443fe360c13fdc84b7980eb82
Signed-off-by: George Keishing <gkeishin@in.ibm.com>
diff --git a/redfish/account_service/test_ipmi_redfish_user.robot b/redfish/account_service/test_ipmi_redfish_user.robot
index 55b2fe3..f26606b 100644
--- a/redfish/account_service/test_ipmi_redfish_user.robot
+++ b/redfish/account_service/test_ipmi_redfish_user.robot
@@ -17,7 +17,10 @@
 ${valid_password2}      0penBmc2
 ${admin_level_priv}     4
 ${operator_level_priv}  3
-${max_num_users}        ${15}
+# Refer:  #openbmc/phosphor-user-manager/blob/master/user_mgr.cpp
+# ipmiMaxUserNameLen = 16;    <-- IPMI
+# systemMaxUserNameLen = 30;  <-- Redfish account users
+${max_num_users}        ${30}
 ${empty_name_pattern}   ^User Name\\s.*\\s:\\s$
 
 ** Test Cases **