Enable sockets extension

Summary:
Notifications Center uses keruald/broker as an abstraction
layer to use a broker.

To connect to RabbitMQ, this library uses php-amqplib.
Recent php-amqplib versions uses the sockets extension.

It appears constants like SOCKET_EAGAIN are now defined
in the sockets extension.

Reference: https://github.com/php-amqplib/php-amqplib/issues/608

Ref T1800

Test Plan:
Build on Dwellers

php -i gives Sockets Support => enabled

Reviewers: dereckson

Reviewed By: dereckson

Subscribers: Nasqueron Docker deployment squad

Tags: Docker images

Maniphest Tasks: T1800

Differential Revision: https://devcentral.nasqueron.org/D2894