Restore doctrine.connections after kernel shutdown

[d-mitrofanov-v]

Hi guys! After updating to 3.10 in my projects, all tests started failing with error:

[Warning] Undefined array key "doctrine.connections" at /var/www/var/cache/test/ContainerKbNY0zx/App_KernelTestDebugContainer.php:1629

The combined changes in persistDoctrineConnections in 3.9.0 and in _getEntityManager in 3.10.0 opened this bug, because Symfony::rebootKernel() removes doctrine.connections to prevent DoctrineBundle from closing the persistent DBAL connection during kernel shutdown and this parameter is never restored, leaving the previous container broken.

Tried to make a minimal change. We remove the parameter in the kernel shutdown phase and restores it afterward. The restoration is also done when kernel shutdown throws. The DBAL connection stays persistent, while the entity manager is still recreated from the current container.

[TavoNiievez]

Hi @d-mitrofanov-v Please create a test similar to:
https://github.com/Codeception/symfony-module-tests/blob/a816870d80a89fa89367bf10e9324315c70b3abd/tests/Functional/IssuesCest.php#L21
in the symfony-module-tests project
to verify the regression you mentioned, implement the change, and ensure that it won't fail again in the future.

[d-mitrofanov-v]

@TavoNiievez hi. Done - Codeception/symfony-module-tests#67

[TavoNiievez]

@d-mitrofanov-v Released as 3.10.1.