QUIC: simplified setting close timer when closing connection.

QUIC: simplified setting close timer when closing connection.

Previously, the timer was never reset due to an explicit check.  The check was
added in 36b59521a41c as part of connection close simplification.  The reason
was to retain the earliest timeout.  However, the timeouts are all the same
while QUIC handshake is in progress and resetting the timer for the same value
has no performance implications.  After handshake completion there's only
application level.  The change removes the check.