Install the allure-pytest package globally in sonic-mgmt docker

[xwjiang-ms]

Why I did it

This fix is to address issue: sonic-net/sonic-mgmt#5280

In the sonic-mgmt Dockerfile, python package allure-pytest is installed after ENV USER $user.
Consequently the package is installed to path /home/$user/.local and is only available to the $user
account. If we use root account in sonic-mgmt docker container to run tests, any script importing
the allure package will fail with ImportError. We need to install the allure-pytest package to global
directory instead of user local directory.

How I did it

Update the sonic-mgmt Dockerfile to ensure that the allure-pytest package is installed to global directory

How to verify it

1. Build a new sonic-mgmt docker image based on the changes.
2. Use sonic-mgmt docker container of the newly built image to run test scripts that depend on the
   allure-pytest package. No ImportError is raised.

Which release branch to backport (provide reason below if selected)

• 201811
• 201911
• 202006
• 202012
• 202106
• 202111

Description for the changelog

Link to config_db schema for YANG module changes

A picture of a cute animal (not mandatory but encouraged)