make unix_socket_connect() for property service a warning

Encourage the use of set_prop macro by making existing
unix_socket_connect(domain, property, init) calls
warn at compile time. When encountering one of these macros,
m4 will emit a deprecated message as follows:

m4: external/sepolicy/adbd.te: 97: deprecated: unix_socket_connect(adbd, property, init) Please use set_prop(adbd, <property name>) instead.

Change-Id: I997fed75d2683933e08db8b9efeecea71523c7c3
Signed-off-by: William Roberts <william.c.roberts@linux.intel.com>