8055111: [TESTBUG] jdk.testlibrary.Utils.removeGcOpts doesn't remove -Xconcgc
Reviewed-by: jmasa, brutisso, sla
'abc'.lastIndexOf('a', 4) = 0
'abc'.lastIndexOf('b', Infinity) = 1
'abc'.lastIndexOf('a', -1) = 0
'abc'.lastIndexOf('a', -Infinity) = 0
'oracle'.lastIndexOf('u') = -1
'hello'.lastIndexOf('l') = 3
'hello'.lastIndexOf('l', 2) = 2
'hello'.lastIndexOf('l', 3) = 3
'hello'.lastIndexOf('l', 1) = -1