[perf test tool] go-ycsb rkv driver writes value not respecting fieldlength setting

[h-w-chen]

when running go-ycsb, setting fieldlength=500, so that the total value length would be 5KB. However, in backend redis, the value saved in char about 3 times more than 5KB (noticing the saved value in word in 5000).

below is part of value retrieved from redis:
char number of such value is 17340

map[field0:[87 78 107 72 121 106 114 113 120 67 82 85 107 74 89 106 105 76 70 102 81 121 100 69 104 70 115 117 116 89 67 76 79 70 117 97 80 80 118 71 71 112 113 113 109 72 78 79 73 70 78 121 112 77 100 90 112 69 112 66 88 67 75 76 79 73 82 98 75 100 110 74 65 121 100 76 77 109 72 85 122 83 122 75 73 83 107 112 111 72 119 119 107 119 98 101 81 73 116 85 90 118 87 78 77 113 66 107 66 103 111 113 80 85 102 79 114 111 109 68 118 67 110 72 86 69 74 104 98 99 119 112 75 103 75 103 111 106 104 104 116 120 85 88 109 117 71 120 112 98 86 117 70 78 85 84 110 84 89 116] field1:[87 103 118 70 76 99 107 89 108 105 107 85 120 117 71 97 106 86 71 75 99 98 80 118 108 107 119 103 116 101 68 79 78 81 105 69 122 85 65 71 72 78 67 87 86 107 81 90 108 111 65 84 117 88 82 116 111 117 73 102 66 97 122 116 67 107 103 121 86 98 105 112 67 73 73 69 99 87 90 86 122 113 99 77 112 77 86 105 79 114 115 118 117 101 104 118 115 109 120 69 74 117 73 121 70 65 78 87 120 80 117 100 109 118 100 70 120 85 87 69 114 74 114 117 89 86 116 106 117 107 74 100 76 109 89 75 106 89 114 107 114 100 106 112 72 109 97 108 66 105 102 85 120 90 69 111 77 70 87 84] field2:[83 109 99 105 113 85 100 79 102 122 122 104 111 88 70 74 120 119 113 72 76 75 122 78 78 114 80 69 88 73
...
67 78 114 105 68 122 115 69 122 88 86 98 81 88 90 99 98 118 87 76 113 97 120 84 86 103 76 113 90 67 103 105 87 97 112 78 101 77 98 115 84 88 90 81 84 119 101 106 115 65 98 104 99 107 70 114 102 104 112 73 105 113 81 83 65 102 67 73 77 69 65 103 88 120 121 117 77 119 72 99 98 69 71 103 74 112 106 75 108 86 120 67 98 99 98 79 106 79 101 84 105 78 78 97 73 122 65 85 89 122 112 100 101 121 69 120 116 66 65 119 114 98 87 112 120 78 69 121 76 100 104 115 80 65 101 97 80 122 82 105 84 105 77 99 69 111 88 102 89 111 69 97 84 83 79 78 78 80 116 75 97 73 122 72 67 76 87 115 120 104 76 80 102 106 106 118 109 85 75 70 89 85 90 119 80 90 74 78 111 117 89 122 79 104 110 86 102 103 69 68 121 80 81 122 122 99 101 99 108 103 67 70 81 105 69 109 66 84 89 114 85 81 88 71 108 102 114 106 119 120 113 113 104 110 106 90 83 104 114 84 97 70 101 82 101 105 84 87 99 86 121 81 82 67 110 87 86 76 115 106 84 65 72 107]]"