Remove res/ari/* content during 'make clean'.

Remove res/ari/* content during 'make clean'.

'make clean' and 'make distclean' can leave behind .o files in the
res/ari/ directory. One observed consequence of this is that running
Asterisk with MALLOC_DEBUG can cause Asterisk to crash immediately on
startup sometimes.

By ensuring that we are making a clean build, we can be sure that stale
files are not being included in the build and causing problems when
build options should have caused files to be re-built.

ASTERISK-25683 #close
Reported by yaron nahum

Change-Id: I1f48baa904d2468eddeefb42ee68a56af7adc7b7