Specs removal incomplete

[holgerfriedrich]

#1958 and #2305 removed most of the specs and the variable servicemix-spec.version.
This currently causes build with Maven 4 to fail, as we still reference ${servicemix-spec.version} in bom/pom.xml.

@jbonofre FYI

[jbonofre]

Good catch. I will clean this up (it works with Maven 3). Thanks!