build-appliance-image: Update to kirkstone head revision

(From OE-Core rev: 0eb8e67aa6833df0cde29833568a70e65c21d7e5)

Signed-off-by: Steve Sakoman <steve@sakoman.com>

meta/recipes-core/images/build-appliance-image_15.0.0.bb

@@ -24,7 +24,7 @@ IMAGE_FSTYPES = "wic.vmdk wic.vhd wic.vhdx"
 
 inherit core-image setuptools3
 
-SRCREV ?= "989cd671cba392b07e48057f02e0b4dd090b48d2"
+SRCREV ?= "73e3b5481bc88b332a198a8ec51a3c43c5f08e7e"
 SRC_URI = "git://git.yoctoproject.org/poky;branch=kirkstone \
            file://Yocto_Build_Appliance.vmx \
            file://Yocto_Build_Appliance.vmxf \