hostname module: add support for Amazon Linux

I added support for Amazon Linux.

In order to add support for Amazon Linux, 
I modified "get_distribution" method of module_utils/basic.py to get "Amazon" distribution,
but I'm not too sure if this is correct.

I found a similar method "get_distribution_facts" on setup module,
but this implementation is very different from module_utils/basic.py's get_distribution.