check for script instead of shell

the shell-provisioner json lookup wrapper is not properly detecting shell scripts.  this PR adjusts the expected output from the ``file`` command.  with this change, tests are now passing:

```
$ ./test.sh 
--- running tests array.sh ---
SUCCESS: output verified: foo bar
SUCCESS: output verified: a b c
SUCCESS: expected failure: non-unique key, multiple matches found
SUCCESS: output verified: a b
SUCCESS: output verified: name conflict
SUCCESS: foo "second element"
--- running tests duplicatekeys.sh ---
SUCCESS: expected failure: non-unique key, multiple matches found
SUCCESS: output verified: first
SUCCESS: output verified: nested
SUCCESS: expected failure: non-unique key, multiple matches found
SUCCESS: output verified: first
SUCCESS: output verified: first
SUCCESS: expected failure: non-unique key, multiple matches found
SUCCESS: output verified: first
SUCCESS: output verified: first
--- running tests nested.sh ---
SUCCESS: output verified: baz
SUCCESS: output verified: baz
SUCCESS: output verified: baz
SUCCESS: expected failure: key not found
--- running tests simplekey.sh ---
SUCCESS: output verified: 456
SUCCESS: output verified: 456
SUCCESS: output verified: a space
SUCCESS: expected failure: key not found
```