[SPARK-7304] [BUILD] Include $@ in call to mvn consistently in make-distribution.sh

Adding the $ allows the caller of this script to supply additional arguments to the mvn command and is consistent with how mvn is being invoked elsewhere in the scripts

Author: Rajendra Gokhale (rvgcentos) <rvg@cloudera.com>

Closes #5846 from palamau/master and squashes the following commits:

e5f2adb [Rajendra Gokhale (rvgcentos)] Add $@ in call to mvn consistently in make-distribution.sh