#### Why I did it
Reset flex counters delay flag on config DB when enable_counters script is called to allow enablement of flex counters in orchagent.
#### How I did it
Push to config DB 'false' value for delay indication when enable_counters script is called before enabling the counters.
#### How to verify it
Observe counters are created when enable_counters script is called.
**- Why I did it**
Align style with slightly modified PEP8 standards (extend maximum line length to 120 chars). This will also help in the transition to Python 3, where it is more strict about whitespace, plus it helps unify style among the SONiC codebase. Will tackle other directories in separate PRs.
**- How I did it**
Using `autopep8 --in-place --max-line-length 120` and some manual tweaks.
**- Why I did it**
As part of moving all SONiC code from Python 2 (no longer supported) to Python 3
**- How I did it**
- Convert enable_counters.py script to Python 3
- Reorganize imports per PEP8 standard
- Two blank lines precede functions per PEP8 standard
**- Why I did it**
We need RIF counters to be enabled by default. Flex Counter does probe for supported counters. If a platform does not support RIF counters, SAI will return NOT_SUPPORTED and Flex Counter will stop polling the counter.
**- How to verify it**
After fresh install rif counter gropup is enabled by default:
$ counterpoll show
Type Interval (in ms) Status
-------------------- ------------------ --------
QUEUE_STAT default (10000) enable
PORT_STAT default (1000) enable
RIF_STAT default (1000) enable
QUEUE_WATERMARK_STAT default (10000) enable
PG_WATERMARK_STAT default (10000) enable
Signed-off-by: Mykola Faryma <mykolaf@mellanox.com>
