RFR: 8266291: (jrtfs) Calling Files.exists may break the JRT filesystem

[Athijegannathan Sundararajan]

Problematic paths that start with /modules/modules prefix are handled properly

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

Commit messages:
 - fixed typos in comments
 - 8266291: (jrtfs) Calling Files.exists may break the JRT filesystem

Changes: https://git.openjdk.java.net/jdk/pull/4022/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=4022&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8266291
  Stats: 36 lines in 2 files changed: 32 ins; 0 del; 4 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4022.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4022/head:pull/4022

PR: https://git.openjdk.java.net/jdk/pull/4022