[jdk17u] RFR: 8277159: Fix java/nio/file/FileStore/Basic.java test by ignoring /run/user/* mount points

[Alex Kasko]

Clean backport of a test fix.

Additional testing:

- [x] checked that updated test passes on Fedora 34 with `/run/user/1000/doc` mount point present (created with `/usr/libexec/xdg-document-portal`)

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Commit messages:
 - Backport b6876649a82bed508d817ccbde1600d00937e4b2

Changes: https://git.openjdk.java.net/jdk17u/pull/313/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk17u&pr=313&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8277159
  Stats: 10 lines in 1 file changed: 10 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk17u/pull/313.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk17u pull/313/head:pull/313

PR: https://git.openjdk.java.net/jdk17u/pull/313