[FIX] web: owl_compatibility: don't call mounted when a rendering is being done

Following commit 637684fb which improved
the conditions under which the ComponentWrapper compatibility layer
should trigger owl's `__callMounted` on all the owl children of a Legacy Widget.

One case was forgotten though: when the current component (wherever it is in the hierarchy)
is rendered BUT another rendering has been initiated meanwhile.

In that case, we shouldn't mark the component as mounted. The owl's fiber.complete algorithm
will take care of calling __callMounted when it finishes.

closes odoo/odoo#75950

Signed-off-by: Simon Genin (ges@odoo) <ges@odoo.com>