fix tpx command line when filtering is enabled
fix tpx command line when filtering is enabled

Summary:
The testpilot command line getdeps generated was not suitable for tpx
when filtering. tpx would consider the passed test filter an
environment variable.

Reorder a few things to at least make filtering work.

Reviewed By: fanzeyi

Differential Revision: D28976061

fbshipit-source-id: 21c45b3a4a59711a2a5da36a1bd11b7b4871ec5d

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