RFR: 8303413: (fs) Ignore polling interval sensitivity modifiers in PollingWatchService

[Brian Burkhalter]

Modify `sun.nio.fs.PollingWatchService` to ignore any polling sensitivity modifiers as done by the other `WatchService`s.

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Commit messages:
 - 8303413: (fs) Ignore polling interval sensitivity modifiers in PollingWatchService

Changes: https://git.openjdk.org/jdk/pull/12795/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12795&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8303413
  Stats: 22 lines in 1 file changed: 1 ins; 8 del; 13 mod
  Patch: https://git.openjdk.org/jdk/pull/12795.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12795/head:pull/12795

PR: https://git.openjdk.org/jdk/pull/12795