Automation RestTest#testEncoding fails when run by maven surefire on non-Linux platforms

This is caused by the fact that org.nuxeo.ecm.automation.server.jaxrs.io.JsonRequestReader uses org.nuxeo.common.utils.FileUtils#read that uses the default platform encoding (system dependent).

The file.encoding system property is only defined to UTF-8 in nuxeo.conf hence when running the tests from maven, the behavior is locale dependent hence the failure.

JsonRequestReader should enforce explicit UTF-8 decoding instead as per: http://tools.ietf.org/html/rfc4627.html

org.nuxeo.common.utils.FileUtils#read should be deprecated to favor: org.apache.commons.io.IOUtils.toString with an explicit charset parameter instead.