Connection Leak During PhaseInstance.Status.TERMINATING

[diegolovison]

Describe the bug
There are issues with connection management when a phase enters PhaseInstance.Status.TERMINATING state. The problems begin from the split responsibility between connection acquisition and release, combined with the stop mechanism during termination.

• PrepareHttpRequestStep - Acquires connection via connectionPool.acquire(false, context)
• SendHttpRequestStep - Sends request via request.send(context.connection, ...)

The connection is released later when the response completes via releasePoolAndPulse()

Problem 1: Connection Acquired But Request Not Sent

This can trigger TERMINATING check before SendHttpRequestStep runs. Connection is stored in context but never used or released.

PrepareHttpRequestStep executes
    ↓
connectionPool.acquire() called [line 89]
    ↓
Connection acquired and stored in context
    ↓
context.accept(connection) calls session.proceed() [line 40]
    ↓
Session checks TERMINATING status [line 265]
    ↓
Session calls stop() [line 269]
    ↓
SendHttpRequestStep NEVER executes
    ↓
Connection NEVER released - LEAK!

Problem 2: Request sent but response handling interrupted

SendHttpRequestStep executes
    ↓
Request sent to server
    ↓
Response starts arriving
    ↓
Phase enters TERMINATING
    ↓
Session.proceed() checks TERMINATING [line 265]
    ↓
Session stops [line 269]
    ↓
Response handler may or may not complete
    ↓
releasePoolAndPulse() may or may not be called
    ↓
Connection may be leaked OR released

To Reproduce
#641

[diegolovison]

If SendHttpRequestStep is skipped or never executed, the associated connection is leaked and unavailable for the next phase. Consequently, the report may show a low request count without explicitly stating the root cause, making this specific scenario extremely difficult to troubleshoot.