Since commit 6c545216, loop restoration coefficients are written inside
tiles data. Since the Wiener and Sgrproj coefficients are
delta-encoded (and tiles must be decoded independently) this means we
must call set_default_wiener and set_default_sgrproj at the start of
encoding and decoding each tile. That patch missed doing so when
encoding large scale tiles (part of the EXT_TILE experiment). This
adds the missing lines.

Note: This caused AV1/AVxEncoderThreadLSTest.EncoderResultTest/3 to
      fail with --enable-ext-tile, which is tracked in bug
      917. Unfortunately, there's something else going wrong that
      means the test is still failing: I'll address that in a separate
      patch.

BUG=aomedia:917

Change-Id: I5bd8e9d7f7a2abd60779abf170185a1c5b090474