Move db_test and external_sst_file_test out of Travis's MAC OS run

Summary:
After we have db_basic_test and external_sst_file_basic_test, we don't need to run db_test and external_sst_file_test in Travis's MAC OS run anymore. Move it out.
Closes https://github.com/facebook/rocksdb/pull/1940

Differential Revision: D4659361

Pulled By: siying

fbshipit-source-id: e64e291

.travis.yml

@@ -46,8 +46,8 @@ before_script:
 
 script:
   - ${CXX} --version
-  - if [[ "${TEST_GROUP}" == 'platform_dependent1' ]]; then OPT=-DTRAVIS V=1 ROCKSDBTESTS_END=external_sst_file_test make -j4 check_some; fi
+  - if [[ "${TEST_GROUP}" == 'platform_dependent1' ]]; then OPT=-DTRAVIS V=1 ROCKSDBTESTS_END=external_sst_file_basic_test make -j4 check_some; fi
-  - if [[ "${TEST_GROUP}" == 'platform_dependent2' ]]; then OPT=-DTRAVIS V=1 ROCKSDBTESTS_START=external_sst_file_test ROCKSDBTESTS_END=checkpoint_test make -j4 check_some; fi
+  - if [[ "${TEST_GROUP}" == 'platform_dependent2' ]]; then OPT=-DTRAVIS V=1 ROCKSDBTESTS_START=external_sst_file_basic_test ROCKSDBTESTS_END=checkpoint_test make -j4 check_some; fi
   - if [[ "${TEST_GROUP}" == 'platform_dependent3' ]]; then OPT=-DTRAVIS V=1 ROCKSDBTESTS_START=checkpoint_test ROCKSDBTESTS_END=db_block_cache_test make -j4 check_some; fi
   - if [[ "${TEST_GROUP}" == '1' ]]; then OPT=-DTRAVIS V=1 ROCKSDBTESTS_START=db_block_cache_test ROCKSDBTESTS_END=comparator_db_test make -j4 check_some; fi
   - if [[ "${TEST_GROUP}" == '2' ]]; then OPT=-DTRAVIS V=1 ROCKSDBTESTS_START=comparator_db_test make -j4 check_some; fi

Makefile

@@ -300,9 +300,7 @@ EXPOBJECTS = $(EXP_LIB_SOURCES:.cc=.o) $(LIBOBJECTS) $(TESTUTIL)
 
 TESTS = \
 	db_basic_test \
-	db_test \
 	db_test2 \
-	external_sst_file_test \
 	external_sst_file_basic_test \
 	auto_roll_logger_test \
 	bloom_test \
@@ -320,6 +318,7 @@ TESTS = \
 	iostats_context_test \
 	db_wal_test \
 	db_block_cache_test \
+	db_test \
 	db_bloom_filter_test \
 	db_iter_test \
 	db_log_iter_test \
@@ -371,6 +370,7 @@ TESTS = \
 	reduce_levels_test \
 	plain_table_db_test \
 	comparator_db_test \
+	external_sst_file_test \
 	prefix_test \
 	skiplist_test \
 	stringappend_test \