s3/php: update to 1.5? version of API

Something like v1.5 of the Amazon PHP library requires the AmazonS3
constructor to be given an array of parameters rather than using
the globals.  More research needs to happen, and particularly
about the v2 API, but this might solve someone's problem with
v1.5 while we do that research.

Signed-off-by: Dan Mick <dan.mick@inktank.com>