icinga: Make all config files belong to icinga:icinga

No reason they should all belong to root.

Also remove the exec{} that munged permissions. Add explicit
modes where required.

Left as root ownership is:
- Executable files
- Files that specifically have a mode set that would not allow
  any access to non-root

Change-Id: I6d95a9b45e868d13b07dd5be42007b263c8f2cf3
Merge "icinga: Make all config files belong to icinga:icinga" into production