Automatically reset received push promises if push promises havee been disabled.

Relevant spec:

This setting can be used to disable server push (Section 8.2). An endpoint MUST NOT send a PUSH_PROMISE frame if it receives this parameter set to a value of 0. An endpoint that has both set this parameter to 0 and had it acknowledged MUST treat the receipt of a PUSH_PROMISE frame as a connection error (Section 5.4.1) of type PROTOCOL_ERROR.

The initial value is 1, which indicates that server push is permitted. Any value other than 0 or 1 MUST be treated as a connection error (Section 5.4.1) of type PROTOCOL_ERROR.

So, the issue is that the default value if "enabled", so the server can actually send push promises before the SETTINGS frame has been received.

The behavior should probably be:

• If the SETTINGS frame that disabled push promises has been ACKed, then receiving a push promise results in a connection error of type PROTOCOL_ERROR.
• If the SETTINGS frame that disabled push promises has been sent but not ACKed, received push promises are automatically reset.

Start by tracing the HTTP/2 SETTINGS handling and PUSH_PROMISE processing described in the issue, using the cited specification as the behavioral reference. Done means an acknowledged disabled setting makes PUSH_PROMISE a PROTOCOL_ERROR, while a sent but unacknowledged setting resets received push promises.