Update test case names DMR/RET/008

In TS-0018:

TP/oneM2M/CSE/DMR/RET/008_CNT/LBL/AT TP/oneM2M/CSE/DMR/RET/008_SUB/LBL/AT TP/oneM2M/CSE/DMR/RET/008_ACP/LBL/AT TP/oneM2M/CSE/DMR/RET/008_GRP/LBL/AT TP/oneM2M/CSE/DMR/RET/008_SCH/LBL/AT TP/oneM2M/CSE/DMR/RET/008_PCH/LBL/AT TP/oneM2M/CSE/DMR/RET/008_TS/LBL/AT

In TTCN-3:

TC_CSE_DMR_RET_008_CNT_AT TC_CSE_DMR_RET_008_SUB_AT TC_CSE_DMR_RET_008_ACP_AT TC_CSE_DMR_RET_008_GRP_AT TC_CSE_DMR_RET_008_SCH_AT TC_CSE_DMR_RET_008_PCH_AT TC_CSE_DMR_RET_008_TS_AT

It is required to add "LBL" to test case names in TTCN-3