android_filesystem_config.h: change ping and run-as

/system/bin/ping no longer requires CAP_NET_RAW, as we're now
using IPPROTO_ICMP. Please see the following for more details:

* http://lwn.net/Articles/443051/
* https://android-review.googlesource.com/52090
* https://android-review.googlesource.com/52072

We can now make ping a normal, unprivileged program.

/system/bin/run-as only requires CAP_SETUID and CAP_SETGID.
Explicitly set the capabilities of this file, and remove
the setuid bit.

This is equivalent to running the following commands:

  * chmod 750 /system/bin/run-as
  * chown root:shell /system/bin/run-as
  * setcap cap_setgid,cap_setuid+ep /system/bin/run-as

Change-Id: I30a5a4588993db68a723b0f6b24b51050dde4f29