Fix brotli decompressor interface usage when reading past the end.

Bortli returns BROTLI_DECODER_RESULT_SUCCESS only when the whole file
was already decompressed, otherwise it will keep returning
BROTLI_DECODER_RESULT_NEEDS_MORE_OUTPUT until enough output space was
provided overall.

This patch fixes the infinite loop caused when trying to decompress
more bytes than available in the uncompressed stream.

Bug: None
Test: Added unittests.
Change-Id: I3a17dc2e9a0b90659161a9315ce27cdb5e90a894