The read http-upgrade-enabled attribute operation acquires the write lock unnecessarily

When we are reading the http-upgrade-enabled, the model is read acquiring the write lock. That could make the operation block until the write lock is released by any other underlying operation that previously has acquired it.

The read handler only reads the value and put it in the response, so taking the write lock here is unnecessary.

This issue affects the ongoing work in WFCORE-4283, there, we could have servers starting with the write lock taken, so it negatively affects to any reading of this attribute.