BUG/MEDIUM: mux-quic: wakeup tasklet to close on error

BUG/MEDIUM: mux-quic: wakeup tasklet to close on error

A recent series of commit have been introduced to rework error
generation on QUIC MUX side. Now, all MUX/APP functions uses
qcc_set_error() to set the flag QC_CF_ERRL on error. Then, this flag is
converted to QC_CF_ERRL_DONE with a CONNECTION_CLOSE emission by
qc_send().

This has the advantage of centralizing the CONNECTION_CLOSE generation
in one place and reduces the link between MUX and quic-conn layer.
However, we must now ensure that every qcc_set_error() call is followed
by a QUIC MUX tasklet to invoke qc_send(). This was not the case, thus
when there is no active transfer, no CONNECTION_CLOSE frame is emitted
and the connection remains opened.

To fix this, add a tasklet_wakeup() directly in qcc_set_error(). This is
a brute force solution as this may be unneeded when already in the MUX
tasklet context. However, it is the simplest solution as it is too
tedious for the moment to list all qcc_set_error() invocation outside of
the tasklet.

This must be backported up to 2.7.