Problem Description & Fix:
When KILL CONNECTION is done on a client that has initiated a
HANDLER READ operation, it results in an assert in debug builds.
The assert happens when sending EOF back to client. During
kill connection, we close the client write end socket descriptor
on the server and this triggers a write error and sets the
diagnostic area of the client connection handle with the
ER_NET_ERROR_ON_WRITE. This failure is not handled in the
HANDLER READ code paths. Hence we send EOF back to client
but the Diagnostics Area is non empty thereby resulting in
an assert in Debug Builds. In release builds, there shall
be no asserts and the client won't see the error.
The fix is to handle the return values of network write error
in the HANDLER .. READ code paths.