Patch setting of AWS credential file environment variable

[salvis2]

@scottyhq I see that you changed the CircleCI action to move credentials to the standard location because the environment variable didn't work: 7cf3c2b#diff-78a8a19706dbd2a4425dd72bdab0502ed7a2cef16365ab7030a5a0588927bf47

I think you need to put export at the beginning of those commands. I fixed this on the hubs in pangeo-data/pangeo-cloud-federation@cede57e#diff-0996279a7b3793d02cc5d648b6034c09effa4e6d2d3e6c82dc1f57179bb0e45fR47.