Bump es version

[learnitall]

Description

This PR bumps elasticsearch client version within our setup.cfg to use elasticsearch>=7.0.0,<8.0.0, (as per documentation spec at https://elasticsearch-py.readthedocs.io/en/v7.14.0a1/), in order to enable Python 3.9 support. Joe and I discussed that we would need to test this change against our ES instances to make sure bumping the client version doesn't break our data ingest.

Fixes

Currently we have elasticsearch client pinned as elasticsearch>=6.0.0,<=7.0.2, however these versions are not compatible with Python 3.9. The following ImportError is observed when trying to invoke snafu on Python 3.9:

snafu/run_snafu.py:20: in <module>
    import elasticsearch
.tox/py39/lib/python3.9/site-packages/elasticsearch/__init__.py:24: in <module>
    from .client import Elasticsearch
.tox/py39/lib/python3.9/site-packages/elasticsearch/client/__init__.py:4: in <module>
    from ..transport import Transport
.tox/py39/lib/python3.9/site-packages/elasticsearch/transport.py:4: in <module>
    from .connection import Urllib3HttpConnection
.tox/py39/lib/python3.9/site-packages/elasticsearch/connection/__init__.py:2: in <module>
    from .http_requests import RequestsHttpConnection
.tox/py39/lib/python3.9/site-packages/elasticsearch/connection/http_requests.py:3: in <module>
    from base64 import decodestring
E   ImportError: cannot import name 'decodestring' from 'base64' (/opt/hostedtoolcache/Python/3.9.6/x64/lib/python3.9/base64.py)

Additionally, I removed the elasticsearch1 module import, as we only have ES >= 7 in our environment, which is supported within the given elasticsearch module itself.

[comet-perf-ci]

Results for SNAFU CI Test

Test	Result	Runtime
snafu/hammerdb	PASS	00:06:40
snafu/smallfile_wrapper	PASS	00:06:11
snafu/flent_wrapper	PASS	00:09:47
snafu/scale_openshift_wrapper	PASS	00:10:43
snafu/sysbench	PASS	00:01:27
snafu/benchmarks/uperf	PASS	00:26:10
snafu/image_pull_wrapper	PASS	00:03:59
snafu/ycsb_wrapper	PASS	00:05:32
snafu/stressng_wrapper	PASS	00:03:21
snafu/fio_wrapper	PASS	00:19:00
snafu/log_generator_wrapper	PASS	00:03:58
snafu/upgrade_openshift_wrapper	PASS	00:00:00
snafu/iperf	PASS	00:05:56
snafu/vegeta_wrapper	PASS	00:05:28
snafu/fs_drift_wrapper	PASS	00:05:55
snafu/pgbench_wrapper	PASS	00:04:19

[whitleykeith]

lgtm

[mohit-sheth]

LGTM