Fix multi-install on BOARD_USES_VENDORIMAGE=false

Vendor apexes will have a realpath under /system/vendor if
BOARD_USES_VENDORIMAGE=false, since /vendor is a symlink to
/system/vendor. system/apex/apexd/apexd_vendor_apex.cpp already handles
that case correctly, so we should update the multi-install code to do
the same check.

Change-Id: I18e836e052cdca7e71888d46bca7309240fab545
1 file changed