Add boost_coroutine to the link list

In preparation for a commit that adds yielding calls to the utils in
libipmid, netipmid needs to be linking against boost_coroutine or it
will fail to build after the commit is merged.

Tested: Builds and runs the same as before, but ldd shows that the new
        binary is linked against boost_coroutine

Change-Id: I2d2c06f6fd529819ee38777547e576acbe06408c
Signed-off-by: Vernon Mauery <vernon.mauery@linux.intel.com>
diff --git a/Makefile.am b/Makefile.am
index dbbbcd8..65f16ba 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -67,6 +67,7 @@
 	$(PHOSPHOR_LOGGING_LIBS) \
 	$(PHOSPHOR_DBUS_INTERFACES_LIBS) \
 	$(LIBIPMID_LIBS) \
+	-lboost_coroutine \
 	-lchannellayer \
 	-luserlayer