kvm: Refactor qemu_kvm_eat_signals

kvm: Refactor qemu_kvm_eat_signals

We do not use the timeout, so drop its logic. As we always poll our
signals, we do not need to drop the global lock. Removing those calls
allows some further simplifications. Also fix the error processing of
sigpending at this chance.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>