run test_update_rowcount_return_defaults only w/ returning

run test_update_rowcount_return_defaults only w/ returning

sane_rowcount_w_returning asserts failure, which will only
occur here if the DBAPI actually uses RETURNING.

as SQLite conditionally supports RETURNING which breaks
rowcount support only if present, limit this test to that
case.

Additionally, newer pysqlites will likely fix the issue so
we will probably want to put a sqlite3_version check as well
once that fix is released.

Change-Id: I065aa181eb48363c1024550ae3622486ae0b4a6e