Fixes the following issue:
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ERROR: test_get_rustc_triplet (test_rust.Testinstance)
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Traceback (most recent call last):
File "/opt/salt/nasqueron-operations/_tests/modules/test_rust.py", line 11, in test_get_rustc_triplet
triplet = rust.get_rustc_triplet()
File "../_modules/rust.py", line 35, in get_rustc_triplet
return __salt__["cmd.shell"]("rustc -vV | sed -ne 's/^host: //p'")
NameError: name '__salt__' is not defined