Run zipfuse in microdroid

zipfuse now runs in microdroid as a service. The source zip file path
and the mount point are fixed to /dev/block/by-name/microdroid-apk and
/mnt/apk, respectively.

To support that, microdroid_payload.json is amended to add
MicrodroidTestAppk.apk to the payload.img file. This eventually should
be done dynamically by the virt manager.

Bug: 186377508
Test: atest MicrodroidHostTestCases
Change-Id: I7a031ad442995dbd3cdc00a51a0e939c1589a7b2
diff --git a/microdroid/init.rc b/microdroid/init.rc
index f9ed986..3c46501 100644
--- a/microdroid/init.rc
+++ b/microdroid/init.rc
@@ -37,6 +37,9 @@
     # Generate linker config based on apex mounted in bootstrap namespace
     update_linker_config
 
+    mkdir /mnt/apk 0755 system system
+    start zipfuse
+
 on init
     # Mount binderfs
     mkdir /dev/binderfs