Add apex_key context for files on product

Set the apex_key context for files in
/product/etc/security/apex/ and
/system/product/etc/security/apex/.

The apexd code is already looking for public keys in these locations,
but the apex_key context needs to be set to make them accessible from
apexd.

Bug: 127690808
Test: manual - verified that key files had proper SE-Linux label
Change-Id: Ib15728fa97eb438ea97a9743a06fa46e4d54f1cd
1 file changed