RFR: 8199407: Skip Rebuild Remset Phase if there are no rebuild candidates [v3]

[Ivan Walulya]

> Hi all,
> 
> Please review this change that skips the rebuild remset phase and the associated updates after rebuild, If during Remark, G1 finds that there are no remembered sets to rebuild.
> 
> Test: tier1-5

Ivan Walulya has updated the pull request incrementally with one additional commit since the last revision:

  change comment

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/3434/files
  - new: https://git.openjdk.java.net/jdk/pull/3434/files/b9233696..41744103

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=3434&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=3434&range=01-02

  Stats: 2 lines in 1 file changed: 1 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3434.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3434/head:pull/3434

PR: https://git.openjdk.java.net/jdk/pull/3434