Fix rpm build script not to set release as version

Release used to indicate number of commits after the version tag
but in case there are no commits it was set to be the version.
This commit will fix it to set to 0.

Signed-off-by: Roi Dayan <roid@mellanox.com>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>