dist/redhat/build_rpm.sh: add dependency for rpmbuild
dist/redhat/build_rpm.sh: add dependency for rpmbuild

Install rpmbuild when it's not installed yet.
Fixes #1651

Signed-off-by: Takuya ASADA <4ebfb6f510af412d6e89fefa3ab96d9c8b5e3fff@scylladb.com>
Message-Id: <1473193430-14792-1-git-send-email-4ebfb6f510af412d6e89fefa3ab96d9c8b5e3fff@scylladb.com>

raphaelsc/scylla,avikivity/scylla,scylladb/scylla,duarten/scylla,avikivity/scylla,duarten/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla,raphaelsc/scylla,raphaelsc/scylla,avikivity/scylla,duarten/scylla