sepolicy: allow rules for apk verify system property

ro.apk_verity.mode was introduced in P on crosshatch. This change
changes the label from default_prop to a new property, apk_verity_prop.

ro.apk_verity.mode is set by vendor_init per build.prop, in order to
honor Treble split.  It is also read by system_server and installd
currently.

Test: verify functioning without denials in dmesg
Bug: 142494008
Bug: 144164497
Change-Id: I1f24513d79237091cf30025bb7ca63282e23c739
6 files changed