Centos 7 specfile updates

[smititelu]

Pre-Submission Checklist

• Commit message has the format required by CONTRIBUTING guide
• Commits are split per component (core, individual modules, libs, utils, ...)
• Each component has a single commit (if not, squash them into one commit)
• No commits to README files for modules (changes must be done to docbook files
  in doc/ subfolder, the README file is autogenerated)

Type Of Change

• Small bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds new functionality)
• Breaking change (fix or feature that would change existing functionality)

Checklist:

• PR should be backported to stable branches
• Tested changes locally
• Related to issue #XXXX (replace XXXX with an open issue number)

Description

Update the specfile for centos 7 to:

• build rabbitmq module package
• exclude kamailio-ims package dependency when installing main kamailio package

[miconda]

I am going to apply 054b865 manually, because the second patch (9010d7e) needs to be discussed. I rushed initially and merged, but then I noticed that the lib/ims depends on libxml2, and by moving it into the core kamailio package, that one becomes dependent of libxml2. Am I right? If yes, this needs to be sorted out in a different way (e.g., make a package kamailio-lib-ims)