RFR: 8327114: Attach in Linux may have wrong behaviour when pid == ns_pid (Kubernetes debug container) [v3]

[Sebastian Lövdahl]

> 8327114: Attach in Linux may have wrong behaviour when pid == ns_pid (Kubernetes debug container)

Sebastian Lövdahl has updated the pull request incrementally with two additional commits since the last revision:

 - Remove unused `SELF_PID_NS`
 - Rewrite in line with suggestion from Larry Cable

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/19055/files
  - new: https://git.openjdk.org/jdk/pull/19055/files/d3e26a0c..c57b4598

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=19055&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=19055&range=01-02

  Stats: 110 lines in 1 file changed: 59 ins; 14 del; 37 mod
  Patch: https://git.openjdk.org/jdk/pull/19055.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19055/head:pull/19055

PR: https://git.openjdk.org/jdk/pull/19055