We're iterating the list, and then freeing the iteration pointer rather
than the list head.

Fixes: 0a9667ec ("hmp: Update info vnc")
Reported-by: Coverity (CID 1421932)
Signed-off-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Message-Id: <20200323120822.51266-1-dgilbert@redhat.com>
Reviewed-by: NPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
(cherry picked from commit d4ff1093)
Signed-off-by: NMichael Roth <mdroth@linux.vnet.ibm.com>