[Avocado-devel] Pass the configuration path by command option, not environment variable

[Wei, Jiangang]

Hi, all

"Running tests in parallel" has been discussed many times.
There are some good ideas that have been put forward,  
but some of them needs more discussion, and some of them are hard to
implement.

So, our team incline to run multiple avocado instances with different
configuration at the same time, each of them execute one case.  by this
way, We can improve test efficiency.

In fact,
avocado had already provided the similar feature by 'VIRTUAL_ENV'.
The method is that manually copy the configuration files at
the /etc/avocado/, and export the backup's path as a variable
'VIRTUAL_ENV'.  
It's very easy to use for users.
But it's not suitable for third party software that call avocado to run
test cases.
so I suggest using the command-line option to replace the environment
variable.
such as,
avocado --base-config-dir xxx

Any suggestions will be helpful to me. Thanks in advance.

Thanks,
wei