RFR: 8309305: sun/security/ssl/SSLSocketImpl/BlockedAsyncClose.java fails with jtreg test timeout [v2]

[Matthew Donovan]

> This PR improves the reliability of the BlockedAsyncClose test by addressing an edge case/race condition between the two test threads. The purpose of the test is to verify that an SSLSocket can be closed if a thread is blocked in a write operation. 
> 
> The test starts a "write" thread that writes data to a socket until the output buffer was filled, causing the write operation to block. The main thread then calls `SSLSocket.close()`. The original code used `Thread.sleep(1000)` to wait for the write-thread to block. However, 1 second isn't always long enough and if the write-thread isn't blocked and the output buffer is full (or almost full), the `socket.close()` call may block when it tries to send the close_notify alert. This is the condition that caused this bug.
> 
> My change uses a Lock to determine if the write thread is blocked. In the write thread, the lock creates a critical section around the `write()` call. The main thread uses `tryLock()` with a timeout to determine that the write() call is taking too long and thus likely blocked. 
> 
> While there, I also updated the test to use the SSLContextTemplate class.

Matthew Donovan has updated the pull request incrementally with one additional commit since the last revision:

  Fixed whitespace.
  
  Co-authored-by: Andrey Turbanov <turbanoff at gmail.com>

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/14378/files
  - new: https://git.openjdk.org/jdk/pull/14378/files/b25620d4..3e3768d0

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=14378&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=14378&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/14378.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14378/head:pull/14378

PR: https://git.openjdk.org/jdk/pull/14378