Current version was always true. Simplify it and make it actually work.
The check for unset variables is not needed also, because the generated
script doesn't have any, except $VERBOSE that must not be set.
TEST PLAN:
Verify that there is no noise (verbose output) from:
$ ./tools/maven/api.sh install bazel
$ ./tools/maven/api.sh install buck
Verify that there is verbose output from:
$ VERBOSE=1 ./tools/maven/api.sh install bazel
$ VERBOSE=1 ./tools/maven/api.sh install buck
Change-Id: I1cd0f4cadfa9cec0217c9bd76f5170c396aa3a12
6b33042bf8