RFR 8228589: BasicJStackTest.java and JcmdOutputEncodingTest.java failing after JDK-8227868

[Schmelter, Ralf]

Hi Severin,

thanks for the review.

> Perhaps there should be a 'testJstackUTF8Output()' which will use the
> thai symbol. Only that test method would use the special-needing-UTF-8-
> marker.

If we remove checking for the marker, the output would be ignored
completely and only the return code is checked. So I would argue to
leave it as it is now. But it would probably make sense to make the
marker string smaller (say ~120 chars). The current length was a result
of the buffer size I originally used (32k, instead of 256 now) and as
we have seen this leads to truncation of the jtr file.

Best regards,
Ralf