sepolicy: add property to generic for loading shsusrd via netmgr

Add property to generic sepolicy for loading shsusrd from netmgr.
Fixes the following-

[   66.051992] type=1107 audit(1549.328:591): uid=0 auid=4294967295
ses=4294967295 subj=u:r:init:s0 msg='avc: denied { set } for
property=persist.vendor.data.shsusr_load pid=921 uid=1001 gid=1001
scontext=u:r:vendor_netmgrd:s0 tcontext=u:object_r:vendor_default_prop:s0
tclass=property_service permissive=0'

CRs-Fixed: 2575687
Change-Id: I32fb31a7f5e64c2095aee081fd855900be0d0701