KVM: nVMX: fix instruction skipping during emulated vm-entry

kvm_skip_emulated_instruction() should not be called after emulating
a VM-entry failure during or after loading guest state
(nested_vmx_entry_failure()). Otherwise the L1 hypervisor is resumed
some number of bytes past vmcs->host_rip.

Fixes: eb277562
Signed-off-by: David Matlack <dmatlack@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>