Attention handler configuration file support

The default behavior of the attention handler can be overriden by
modifying the config file contents. The behavior can also be defined
by the associated build option. The default behavior remains
unchanged. The intent of this change is to allow other components to
change the attention handler behavior by updating the configuration file
and restarting the attention handler service.

Signed-off-by: Ben Tyner <ben.tyner@ibm.com>
Change-Id: I8f73004c926a3a070c5feb690ee5684429f922c5
diff --git a/attn/attn_config.in b/attn/attn_config.in
new file mode 100644
index 0000000..94d7842
--- /dev/null
+++ b/attn/attn_config.in
@@ -0,0 +1 @@
+CONFIG=@ATTN_CONFIG@