cardiff: Adding missing disk's summary

The disk summary was missing some disks and the disk name didn't got
printed at all.

A typical output looks like :

Group 1 : Checking logical disks perf
standalone_randwrite_4k_IOps   sda: SUMMARY :  14 consistent hosts with   660.00 IOps as average value and    25.74 standard deviation
standalone_randwrite_4k_IOps   sda: SUMMARY :   1 curious    hosts with  1038.00 IOps as average value and     0.00 standard deviation
standalone_randwrite_4k_IOps   sdb: SUMMARY :  14 consistent hosts with   660.00 IOps as average value and    25.74 standard deviation
standalone_randwrite_4k_IOps   sdb: SUMMARY :   1 curious    hosts with  1038.00 IOps as average value and     0.00 standard deviation
standalone_randwrite_4k_IOps   sdb: SUMMARY :  14 unstable   hosts with   660.00 IOps as average value and    25.74 standard deviation
standalone_randread_4k_IOps    sda: SUMMARY :  15 consistent hosts with   303.80 IOps as average value and     4.85 standard deviation
standalone_randread_4k_IOps    sdb: SUMMARY :  15 consistent hosts with   303.80 IOps as average value and     4.85 standard deviation
standalone_read_1M_IOps        sda: SUMMARY :  15 consistent hosts with   183.03 IOps as average value and     2.90 standard deviation
standalone_read_1M_IOps        sdb: SUMMARY :  15 consistent hosts with   183.03 IOps as average value and     2.90 standard deviation
standalone_write_1M_IOps       sda: SUMMARY :  15 unstable   hosts with     7.50 IOps as average value and     0.45 standard deviation
standalone_write_1M_IOps       sdb: SUMMARY :  14 consistent hosts with     7.57 IOps as average value and     0.37 standard deviation
standalone_write_1M_IOps       sdb: SUMMARY :   1 curious    hosts with     6.50 IOps as average value and     0.00 standard deviation
standalone_write_1M_IOps       sdb: SUMMARY :  15 unstable   hosts with     7.50 IOps as average value and     0.45 standard deviation
simultaneous_randwrite_4k_IOps sda: SUMMARY :  15 unstable   hosts with   865.83 IOps as average value and   243.24 standard deviation
simultaneous_randwrite_4k_IOps sdb: SUMMARY :  30 unstable   hosts with   865.83 IOps as average value and   243.24 standard deviation
simultaneous_randread_4k_IOps  sda: SUMMARY :  15 consistent hosts with   326.17 IOps as average value and     5.60 standard deviation
simultaneous_randread_4k_IOps  sdb: SUMMARY :  15 consistent hosts with   326.17 IOps as average value and     5.60 standard deviation
simultaneous_read_1M_IOps      sda: SUMMARY :  15 consistent hosts with   184.50 IOps as average value and     1.43 standard deviation
simultaneous_read_1M_IOps      sdb: SUMMARY :  15 consistent hosts with   184.50 IOps as average value and     1.43 standard deviation
simultaneous_write_1M_IOps     sda: SUMMARY :  15 unstable   hosts with    41.63 IOps as average value and     9.09 standard deviation
simultaneous_write_1M_IOps     sdb: SUMMARY :  30 unstable   hosts with    41.63 IOps as average value and     9.09 standard deviation