qemu_migration_params: Refactor qemuMigrationParamsReset

qemu_migration_params: Refactor qemuMigrationParamsReset

Because qemuMigrationParamsReset used to call qemuMigrationParamsApply
for resetting migration capabilities and parameters, it did not work
well since commit v5.1.0-83-ga1dec315c9 which only allowed capabilities
to be set from an async job. However, when reconnecting to running
domains after daemon restart we do not have an async job. Thus the
capabilities were not properly reset in case the daemon was restarted
during an ongoing migration. We need to avoid calling
qemuMigrationParamsApply to make sure both parameters and capabilities
can be reset by a normal job.

https://bugzilla.redhat.com/show_bug.cgi?id=2107892

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>