x86/HVM: don't mark external IRQs as pending when vLAPIC is disabled

x86/HVM: don't mark external IRQs as pending when vLAPIC is disabled

In software-disabled state an LAPIC does not accept any interrupt
requests and hence no IRR bit would newly become set while in this
state. As a result it is also wrong for us to mark IO-APIC or MSI
originating vectors as having a pending request when the vLAPIC is in
this state. Such interrupts are simply lost.

Introduce (IO-APIC) or re-use (MSI) a local variable to help
readability.

Fixes: 4fe21ad3712e ("This patch add virtual IOAPIC support for VMX guest")
Fixes: 85715f4bc7c9 ("MSI 5/6: add MSI support to passthrough HVM domain")
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>