Enable region sourcing from efs-utils configuration file and fix stunnel exec path issue in openSUSE

* Support new option: netns, enable file system to mount in given network namespace
* Support new option: awscredsuri, enable sourcing iam authorization from aws credentials relative uri
* List openssl and util-linux as package dependency for IAM/AP authorization and command nsenter to mount file system to given network namespace

* Support retrieving metadata using IMDSv2
* Allow specification of interval for certificate renewal in the config file
* Fix retrieval of instance metadata on ECS

* Ensure that certificate renewals always use the original credentials source
* Include file system ID in all client TLS certificates
* Updates to man page and README

Fixes the mount issue with full DNS name in the AWS China Regions; Upgrades unit test coverage version dependency to enable accurate python3.8 coverage test

Added region localization, Integrate repository with CircleCI to enable package build visualization, Unit tests bug fixes for python3.5

Includes a mount helper utility (mount.efs), an associated watchdog
process, unit tests, and build scripts.

The utility simplifies mounting and using EFS file systems and
optionally enables clients to mount over a TLS tunnel.