Add remount capability to Zygote.

This is a consequence of https://googleplex-android-review.googlesource.com/#/c/278069/

Change-Id: I9b310860534a80e7145950f6c632cf5ba0ad56a7

zygote.te

@@ -37,6 +37,7 @@ allow zygote sdcard_type:dir { write search setattr create add_name mounton };
 dontaudit zygote self:capability fsetid;
 allow zygote tmpfs:dir { write create add_name setattr mounton search };
 allow zygote tmpfs:filesystem mount;
+allow zygote labeledfs:filesystem remount;
 
 # Handle --invoke-with command when launching Zygote with a wrapper command.
 allow zygote zygote_exec:file { execute_no_trans open };