ns: TC_sns_bss_change_weight_timeout: fix expected SNS_SIZE PDU

Allow to work with IPv4 and IPv6 endpoints and only expected known required
fields (e.g. NSEI and rst_flag).

Related: OS#5036
Change-Id: I60f669d7c8838d460a14c6604c4375a8d47f5149
1 file changed