Decoder: Moved end of pic processing to end of decode call

ih264d_end_of_pic() was called after parsing slice of a new picture.
This is now being done at the end of decode of the current picture.
decode_gaps_in_frame_num which needs frame_num of new slice is now
done after decoding frame_num in new slice.

This helps in handling errors in picaff streams with gaps in frames

Bug: 33588051
Bug: 33641588
Bug: 34097231
Change-Id: I1a26e611aaa2c19e2043e05a210849bd21b22220
