Keychain password prompts happen after machine lock/unlock cycle even with QT_SSL_USE_TEMPORARY_KEYCHAIN

The mitigation for QTBUG-56102 causing unwanted password prompts appears to break after a machine lock/unlock or sleep/wake cycle. I believe macOS calls SecKeychainLockAll() when the machine returns to the lock screen to lock all of the user's active keychains. As a result, Qt's temporary keychain is also locked, causing endless unwanted password prompts when it tries to use keys and prompting the user for a password they could not possibly have (since the QSslSocket's EphemeralSecKeychain object generates it internally).

I believe this issue can be fixed by calling SecKeychainGetStatus() prior to using the temporary keychain and using SecKeychainUnlock() if the temporary keychain is locked. This does leave a little window where a password prompt could still be generated if the keychain is locked at just the right time, but it's certainly better than an endless stream of password prompts which I get now.

For an even more comprehensive solution, SecKeychainSetUserInteractionAllowed() can block all password prompts (turning the race condition into a SecPKCS12Import() failure rather than a blocking password prompt).