RFR: 8277159: Fix java/nio/file/FileStore/Basic.java test by ignoring /run/user/* mount points

[Alex Kasko]

…/user/* mount points

The fix to the test is the same as in #5136 . The possible problem with this test was identified in [this comment](https://github.com/openjdk/jdk/pull/5136#issuecomment-900402107), however FileSystemException is thrown instead of NoSuchFileException in this case, thus the special check for "/run/user" is added.

-------------

Commit messages:
 - 8277159: Fix java/nio/file/FileStore/Basic.java test by ignoring /run/user/* mount points

Changes: https://git.openjdk.java.net/jdk/pull/6399/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6399&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8277159
  Stats: 11 lines in 1 file changed: 10 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6399.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6399/head:pull/6399

PR: https://git.openjdk.java.net/jdk/pull/6399