Add policy for ping.

Change-Id: I168f681d8c67f470b6e639f0b1bf39346c4eb396
Allow drmserver to read the wv keys.

Bug: 8539042
Change-Id: I31e7a3ae6ba783b78c3b38756966950a20f2f2aa
ping: add exec_type

Change-Id: Ib3ded3e61cc5130bd68f4a7044c58f2dbbdfa20d