use the built integration.test binary

[MHBauer]

as part of invoking make test we build the test,
as part of running the test we build the test again.

if you could build the test the first time, why would this change, so just use the existing output.

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[jberkhahn]

Seems reasonable. However, looking back it seems we used to do a bit of custom set up inside integration.sh. Is that uncessessary now and in the future?

[MHBauer]

the build-integration target is always called, and it skips all of the details of integration.sh, and nobody has complained so far, so I figured it was okay to dump it.

[carolynvs]

LGTM

[jpeeler]

The -i flag was my concern in the wrapper script and since that's not being used, this change LGTM.