SIOM mode Switch credentials

Each Lenovo Flex Switch using SIOM mode (requires 8.4.3 firmware or greater) can be accessed only using CMM LDAP credentials, or the external LDAP credentials configured on the CMM, if any (e.g. LXCA credentials under Centralized User Management). Furthermore, valid SNMPv3 accounts of the switch are determined by the Centralized User Management flag settings on the CMM: if enabled, valid credentials are those used configured on the CMM. If disabled, valid credentials are those set up locally on the switch. This information applicable to Lenovo switches only.