media{codec, extractor}: update seccomp policy.

Update the mediacodec and mediaextractor seccomp policies to allow
getpid and gettid, which started being used after this CL:
https://android-review.googlesource.com/c/390273/

Bug: http://b/38508369
Test: debuggerd -b `pidof media.codec`
Test: debuggerd -b `pidof media.extractor`
Change-Id: I1be61f645fa475856fa814747a5740689492aa2b