[thci] fix failing Thread 1.1 Cert Tests (#7199)
[thci] fix failing Thread 1.1 Cert Tests (#7199)

This commit fixes tests of 1.1 certification: SED 6_5_1, 6_5_2, 6_5_3,
9_2_8; Commissioner 9_2_4; Leader 9_2_11
openthread/openthread,srickardti/openthread,openthread/openthread,openthread/openthread,jwhui/openthread,jwhui/openthread,abtink/openthread,srickardti/openthread,srickardti/openthread,jwhui/openthread,openthread/openthread,abtink/openthread,abtink/openthread,jwhui/openthread,abtink/openthread,srickardti/openthread