Similar to the way we test osmo-bts, add simple dispatcher script which
calls appropriate test depending on a given parameter. This will allow
to simplify the job description. While at it, also rename jenkins-arm.sh
-> jenkins_arm.sh to match the OsmoBTS.
The older scripts are preserved for compatibility and shall be removed
once we update job description in osmo-ci.
Change-Id: I2955e866bce4f000a53369bd601a346c36c82468