Description:
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in RINIT, mysqlnd_ms tries to parse the plugin config file.

Starting from 1.1, it uses a JSON config file, but the error message when the 
file is not found still talks about INI file, leading to confusion. The ini param 
still is "mysqlnd_ms.ini_file" , and should be renamed to "mysqlnd_ms.json_file"

Also, it is *very* annoying that if there is a parse error while parsing JSON 
config file, nothing is reported in user land, and the process just keeps on 
failing later on other errors

Test script:
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Give a wrong plugin config file (mysqlnd_ms.ini_file) and see the error message talking about INI file

Give a right plugin config file ((mysqlnd_ms.ini_file), but containing a parse error in the JSON syntax

Expected result:
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Correct error messages

Actual result:
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Incorrect error messages