RFR:8235211: serviceability/attach/RemovingUnixDomainSocketTest.java fails with AttachNotSupportedException: Unable to open socket file

[Liu, Xin]

Hi, 8u Maintainers,

Can I get reviewed on this issue? This is the follow-up fix of
JDK-8225690, which has been backported to jdk8u. We found that it may
encounter an unrecoverable safepoint deadlock It's hard to simulate the
deadlock in test, but we describe the scenario in the PR. please take a
look.

Bug: https://bugs.openjdk.java.net/browse/JDK-8235211
PR on github: https://github.com/openjdk/jdk8u-dev/pull/32

thanks,
--lx