Revert /proc/net related changes

Revert the tightening of /proc/net access. These changes
are causing a lot of denials, and I want additional time to
figure out a better solution.

Addresses the following denials (and many more):

  avc: denied { read } for comm="SyncAdapterThre" name="stats" dev="proc" ino=X scontext=u:r:untrusted_app:s0:c512,c768 tcontext=u:object_r:proc_net:s0 tclass=file
  avc: denied { read } for comm="facebook.katana" name="iface_stat_fmt" dev="proc" ino=X scontext=u:r:untrusted_app:s0:c512,c768 tcontext=u:object_r:proc_net:s0 tclass=file
  avc: denied { read } for comm="IntentService[C" name="if_inet6" dev="proc" ino=X scontext=u:r:untrusted_app:s0:c512,c768 tcontext=u:object_r:proc_net:s0 tclass=file
  avc: denied { read } for comm="dumpstate" name="iface_stat_all" dev="proc" ino=X scontext=u:r:dumpstate:s0 tcontext=u:object_r:proc_net:s0 tclass=file

This reverts commit 0f0324cc
and commit 99940d1a

Bug: 9496886
Bug: 19034637
Change-Id: I436a6e3638ac9ed49afbee214e752fe2b0112868