plugins/loader: fix deadlock when resetting/uninstalling a plugin

plugins/loader: fix deadlock when resetting/uninstalling a plugin

Reported and fixed by Dmitry Kurakin.

Fixes: https://gitlab.com/qemu-project/qemu/-/issues/2901
Signed-off-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Message-Id: <20250404032027.430575-2-pierrick.bouvier@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
(cherry picked from commit c07cd110a1824e2d046581af7375f16dac26e96f)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>