private File mkDir(File file) {
		if (file.mkdirs()) {
			LOGGER.info("{} is created.", file.getPath());
		}
		return file;
	}
Get the sub directory for the given perftest.

@param perfTest perfTest
@param subPath  subPath
@return {@link PerfTest} sub directory.
ngrinder-controller/src/main/java/org/ngrinder/common/model/Home.java