Optimize the common case of injecting an interrupt into a vcpu after a HLT
by explicitly moving it out of the interrupt shadow. The hypervisor is done
"executing" the HLT and by definition this moves the vcpu out of the
1-instruction interrupt shadow.

Prior to this change the interrupt would be held pending because the VMCS
guest-interruptibility-state would indicate that "blocking by STI" was in
effect. This resulted in an unnecessary round trip into the guest before
the pending interrupt could be injected.

Reviewed by:	grehan


git-svn-id: svn+ssh://svn.freebsd.org/base/head@271451 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f