RFR: 8284686: Interval of < 1 ms disables ExecutionSample events

[Johannes Bechberger]

Fixes the issue by rounding the period interval to the next full millisecond larger than zero.

The following from the bug report works now:

java -XX:StartFlightRecording=filename=flight.jfr,jdk.ExecutionSample#period=999us CLASS_FILE; jfr print --events jdk.ExecutionSample flight.jfr

It considers the period to be `1ms`, producing the recording as expected.

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

Commit messages:
 - 8284686: Interval of < 1 ms disables ExecutionSample events

Changes: https://git.openjdk.java.net/jdk/pull/8183/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8183&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8284686
  Stats: 3 lines in 2 files changed: 2 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8183.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8183/head:pull/8183

PR: https://git.openjdk.java.net/jdk/pull/8183