Merge remote-tracking branch 'remotes/armbru/tags/pull-qapi-2021-03-05' into staging

Merge remote-tracking branch 'remotes/armbru/tags/pull-qapi-2021-03-05' into staging

QAPI patches patches for 2021-03-05

# gpg: Signature made Fri 05 Mar 2021 14:42:18 GMT
# gpg:                using RSA key 354BC8B3D7EB2A6B68674E5F3870B400EB918653
# gpg:                issuer "armbru@redhat.com"
# gpg: Good signature from "Markus Armbruster <armbru@redhat.com>" [full]
# gpg:                 aka "Markus Armbruster <armbru@pond.sub.org>" [full]
# Primary key fingerprint: 354B C8B3 D7EB 2A6B 6867  4E5F 3870 B400 EB91 8653

* remotes/armbru/tags/pull-qapi-2021-03-05:
  qapi: Fix parse errors for removal of null from schema language
  qapi: Remove QMP events and commands from user-mode builds
  qga: Utilize QAPI_LIST_APPEND in qmp_guest_network_get_interfaces
  error: Fix "Converting to ERRP_GUARD()" doc on "valid at return"

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>