BUG/MEDIUM: stconn: Don't perform L7 retries with large buffer

BUG/MEDIUM: stconn: Don't perform L7 retries with large buffer

L7 retries are buggy when a large buffer is used on the request channel. A
memcpy is used to copy data from the request buffer into the L7 buffer. The
L7 buffer is for now always a standard buffer. So if a larger buffer is
used, this leads to a buffer overflow and crash the process.

The Best way to fix the issue is to disable L7 retries when a large buffer
was allocated for the request channel. In that case, we don't want to
allocate an extra large buffer.

No backport needed.