fix(sysbench): fix extraction of test-name option

The `=` seems to be missing in the pattern.  This pattern was in this
form from the beginning when the sysbench completion is introduced in
commit 77b78b3.  With the current implementation, `--test`,
`--testxxxx`, etc. can also match, and $test becomes `--test`,
`--testxxxx`, etc.  This results in the later evaluation of
`--test=--test` or `--test=--testxxxx`, which doesn't seem to be
correct.  Therefore, `=` is suspected to be missing.

completions/sysbench

@@ -104,7 +104,7 @@ _comp_cmd_sysbench()
     local i test="" has_test=""
     for ((i = 1; i < ${#words[@]} - 1; i++)); do
         # TODO --test= is deprecated, bare test name preferred
-        if [[ ${words[i]} == --test* ]]; then
+        if [[ ${words[i]} == --test=* ]]; then
             test=${words[i]#*=}
             has_test=set
             break