Give crash_dump CAP_SYS_PTRACE.

CAP_SYS_PTRACE is needed to ptrace processes that have capabilities
greater than their bounding set. Eventually, this will still be an
improvement, because we can ptrace attach, and then turn on a seccomp
filter that blocks further attaches.

Bug: http://b/34694637
Test: debuggerd `pidof system_server`
Change-Id: I4b9da164ec1fbb5060fdba590e886ac24b6a0785