TT#151402 Start using '/ngcp-data/cache' via symlink

We need to change the place for storing temporary and constant
audio files (caching of audio files).

Newly used paths:
- /ngcp-data/ngcp-sems

This path will be from now on reachable via the symbolic link:
- /var/cache/ngcp-sems

Change-Id: Ia1a120aaa256498d541611f2115570e1abe8ea90

debian/ngcp-sems.tmpfiles

@@ -1,4 +1,5 @@
 d /run/ngcp-sems 0755 sems sems
-d /var/cache/ngcp-sems 0755 sems sems
-d /var/cache/ngcp-sems/audio_cache 0755 sems sems
-d /var/cache/ngcp-sems/callingcard 0755 sems sems
+d /ngcp-data/cache/ngcp-sems 0755 sems sems
+d /ngcp-data/cache/ngcp-sems/audio_cache 0755 sems sems
+d /ngcp-data/cache/ngcp-sems/callingcard 0755 sems sems
+L+ /var/cache/ngcp-sems - - - - /ngcp-data/cache/ngcp-sems