Reset segment id if we decide not to update segment map
Reset segment id if we decide not to update segment map

This avoids potential encoder and decoder mismatch.

Change-Id: I5282d3e168afc6193033ad3fce8fbc35618ab2f5
(cherry picked from commit 386e4ba2f0c5e95bf2ad6042cae46a9ba07a5141)

webmproject/libwebp,PKRoma/libwebp,PKRoma/libwebp,PKRoma/libwebp,webmproject/libwebp,PKRoma/libwebp,webmproject/libwebp,PKRoma/libwebp,webmproject/libwebp,PKRoma/libwebp,webmproject/libwebp