fluster: Fix the result parser for shorter suite names
A newly added vectors suite named JVT-MVC is shorter that the minimal
suite name length for the fluster test results output.
So, the fluster output adds spaces so that the column width is at least
the size of its header: [TEST SUITE]
.
Because of that, the regexp has to allow padding spaces to match the output and, because the test suite name is not used later, we can just match any characters between the '[' and ']' chars.
Note that it works without using look ahead as it is the only place using the '[' and ']' chars.