presence: Use shared JSON config file finding & loading header

Use the shared JSON config determination header for loading its
JSON configuration file.

Tested:
    run phosphor-fan-presence-tach can find and load config.json from
    /usr/share/phosphor-fan-presence/presence and
    /etc/phosphor-fan-presence/presence/ in witherspoon qemu

Change-Id: I5c4fdf7d96de7c956ca24b4a5751911cc1bf1f03
Signed-off-by: Jolie Ku <jolie_ku@wistron.com>
diff --git a/presence/Makefile.am b/presence/Makefile.am
index a9e62d3..d67f287 100644
--- a/presence/Makefile.am
+++ b/presence/Makefile.am
@@ -12,7 +12,7 @@
 	psensor.cpp \
 	tach.cpp \
 	tach_detect.cpp \
-	json_config.cpp
+	json_parser.cpp
 
 phosphor_fan_presence_tach_LDADD = \
 	$(SDBUSPLUS_LIBS) \