Fix pre_release tests

2 fixes:
- The no-ssl telemetry tests should always run in debug tests
- Run explain on a query instead of the query because this query
  runs out of memory in our underpowered arm tests and the bug
  we are looking is in the planner anyway.

.travis.yml

@@ -29,7 +29,7 @@ install:
   - docker exec -it pgbuild /bin/bash -c "chown -R postgres:postgres /postgres/"
 script:
   # First build without OpenSSL
-  - docker exec -it pgbuild /bin/sh -c "cd /build/debug-nossl && cmake .. -DUSE_OPENSSL=false -DPG_SOURCE_DIR=/postgres -DCMAKE_BUILD_TYPE=Debug ${OTHER_CMAKE_FLAGS:-} && make install && chown -R postgres:postgres /build/debug-nossl/"
+  - docker exec -it pgbuild /bin/sh -c "cd /build/debug-nossl && cmake .. -DUSE_OPENSSL=false -DPG_SOURCE_DIR=/postgres ${OTHER_CMAKE_FLAGS:-} -DCMAKE_BUILD_TYPE=Debug && make install && chown -R postgres:postgres /build/debug-nossl/"
   # Run only telemetry test to see that it works without OpenSSL
   - ${RETRY_PREFIX} docker exec -u postgres -it pgbuild /bin/sh -c "make -C /build/debug-nossl installcheck TESTS=telemetry PG_REGRESS_OPTS='--temp-instance=/tmp/pgdata'"
   # Now build with OpenSSL

tsl/test/sql/include/transparent_decompression_undiffed.sql

@@ -19,7 +19,7 @@ FROM _timescaledb_catalog.chunk chunk
 INNER JOIN _timescaledb_catalog.hypertable hypertable ON (chunk.hypertable_id = hypertable.id)
 WHERE hypertable.table_name = 'readings' and chunk.compressed_chunk_id IS NULL;
 
-SELECT t.fleet as fleet, min(r.fuel_consumption) AS avg_fuel_consumption
+EXPLAIN (costs off) SELECT t.fleet as fleet, min(r.fuel_consumption) AS avg_fuel_consumption
 FROM tags t
 INNER JOIN LATERAL(SELECT tags_id, fuel_consumption FROM readings r WHERE r.tags_id = t.id ) r ON true
 GROUP BY fleet;