The external interrupt events only can be inject if RFLAGS.IF = 1 and no
blocking by both STI and MOV SS. If met this scenario, we need to enable
"interrupt-window exiting" for injection in next VMEXIT.
Tracked-On: #1189
Signed-off-by: Yu Wang <yu1.wang@intel.com>
Acked-by: Anthony Xu <anthony.xu@intel.com>