[packaging] Fix rpm rc versioning

Currently if a tag is formatted in the standard RC format for PL, e.g. appended with '-rcX', the rpm versioning will create a file with an extra '.' in it between version and release, e.g. 'puppetdb-1.1.0.-0.1rc1.el5.src.rpm'. This commit chops the dot from rpm.

Signed-off-by: Moses Mendoza <moses@puppetlabs.com>