RFR: 8290005: com/sun/jndi/ldap/LdapCBPropertiesTest.java failling with NullPointerException [v4]

[Matthew Donovan]

> In this PR, I added methods to the TransportContext class to synchronize access to the handshakeContext field. I also updated locations in the code that rely on the handshakeContext field to not be null to use the synchronized methods.
> 
> Thanks

Matthew Donovan has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains five additional commits since the last revision:

 - I missed a method that needed updating
 - Merge branch 'master' into socket-close-null
 - made handshake context lock final
 - using try/finally in terminateHandshakeContext and using local context variable in all places it should be
 - 8290005: com/sun/jndi/ldap/LdapCBPropertiesTest.java failling with NullPointerException

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/13742/files
  - new: https://git.openjdk.org/jdk/pull/13742/files/92a48a70..e95cef8e

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13742&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13742&range=02-03

  Stats: 263186 lines in 4286 files changed: 195335 ins; 39118 del; 28733 mod
  Patch: https://git.openjdk.org/jdk/pull/13742.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13742/head:pull/13742

PR: https://git.openjdk.org/jdk/pull/13742