RFR: 8280928: os::Linux::get_tick_information is inaccurate if the guest fields are non-zero

[Mitsuru Kariya]

Removed `guestNiceTicks` from `os::Linux::get_tick_information` because the guest field in `/proc/stat` is already added to the user field in `/proc/stat` inside the linux kernel.

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Commit messages:
 - 8280928: os::Linux::get_tick_information is inaccurate if the guest fields are non-zero

Changes: https://git.openjdk.java.net/jdk/pull/7303/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7303&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8280928
  Stats: 8 lines in 1 file changed: 0 ins; 3 del; 5 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7303.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7303/head:pull/7303

PR: https://git.openjdk.java.net/jdk/pull/7303