audiopolicy: capengine: fix missing comma when chaining compound rules

When chaining compound rule closed by "}", a comma is added to notify the continuation. This comma was missing, hence breaking rule parsing.

Bug: 388404113
Test: m

Change-Id: I3f90c5e91263a4ad1a78a91ea8c667f2e51b7d9b
Signed-off-by: François Gaffie <francois.gaffie@ampere.cars>