Create an S3 client based on local storage

[hicder]

Right now, the unit tests are not able to run because we use actual S3 storage for tests. We want to mock the S3 storage using local storage so that unit test run faster.

In this PR, I created a class TestS3ClientWrapper which extends AwsS3ClientWrapper. Also, update run_tests.sh to disable all networking for docker container to confirm that this test runs locally.

Before my changes, run_tests.sh never completes. With my changes, run_tests.sh completes all tests in 15 minutes. Breakdown as followed:

• db_test2

[----------] Global test environment tear-down
[==========] 137 tests from 6 test cases ran. (55334 ms total)
[  PASSED  ] 137 tests.

• db_basoc_test

[----------] Global test environment tear-down
[==========] 154 tests from 6 test cases ran. (207756 ms total)
[  PASSED  ] 154 tests.

• env_basic_test

[----------] Global test environment tear-down
[==========] 15 tests from 4 test cases ran. (24 ms total)
[  PASSED  ] 15 tests.

• cloud_manifest_test

[----------] Global test environment tear-down
[==========] 1 test from 1 test case ran. (7 ms total)
[  PASSED  ] 1 test.

• db_cloud_test

[----------] Global test environment tear-down
[==========] 23 tests from 1 test case ran. (64610 ms total)
[  PASSED  ] 23 tests.

• db_test

[----------] Global test environment tear-down
[==========] 165 tests from 3 test cases ran. (659752 ms total)
[  PASSED  ] 165 tests.

[hicder]

CircleCI passes! https://app.circleci.com/pipelines/github/rockset/rocksdb-cloud/5/workflows/c36670ce-0647-40a1-9f58-f1c63123b4c9/jobs/5

[hicder]

I'll remove Travis eventually. CircleCI seems to be much faster.

[hicder]

Once this PR is merged, we'll require CircleCI build to pass before merging. I think it will make merging much safer.

[igorcanadi]

Could we move this implementation to the test file, so that we don't clutter the production binary?

[igorcanadi]

Do we also need an integration test that actually uses S3?

[hicder]

@mrambacher is going to have a similar PR that mocks the StorageProvider, instead of mocking the S3Client in a week, so I'll put this PR on hold.