When calling show_chunks or drop_chunks without specifying
a particular hypertable TimescaleDB iterates through all
existing hypertables and builds a list. While doing this
it adds the internal '_compressed_hypertable_*' tables
which leads to incorrect behaviour of
ts_chunk_get_chunks_in_time_range function. This fix
filters out the internal compressed tables while scanning
at ts_hypertable_get_all function.
