stagefright: don't fail MediaCodec.configure if clients use store-meta key

Even though storing metadata is not supported in MediaCodec.configure and
is only meant to be used by Stagefright recorder, don't fail configure.

Bug: 31986922
Change-Id: Id9f083be6e857e7a0d8d4a74159be5b8894e28be
(cherry picked from commit ae52fd38)