Add build option to disable daemon control via IPC

Added a build option (nlmode) to disable the attention handler runtime
control support (IPC). Until the IPC based start/stop controls are
working correctly the build will default to nlmode enabled. The
attention handler can still be stopped and started via normal systemctl
methods.

Signed-off-by: Ben Tyner <ben.tyner@ibm.com>
Change-Id: I8913fb441fd696d81ffc04b464601238068c3131
diff --git a/meson_options.txt b/meson_options.txt
index 0fc2767..b1c8b8f 100644
--- a/meson_options.txt
+++ b/meson_options.txt
@@ -1 +1,2 @@
 option('tests', type: 'feature', description: 'Build tests')
+option('nlmode', type: 'feature', description: 'no run-time control')