If a nested page fault happens during emulation, we will inject a vmexit,
not a page fault.  However because writeback happens after the injection,
we will write ctxt->eip from L2 into the L1 EIP.  We do not write back
if an instruction caused an interception vmexit---do the same for page
faults.
Suggested-by: NGleb Natapov <gleb@kernel.org>
Reviewed-by: NGleb Natapov <gleb@kernel.org>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>