presence: Fix and run fallbacktest

The fan presence tests didn't get enabled properly on the move to meson.
Fix that so they run, and then also fix the compile errors in the
testcase due to code that has changed since it had been disabled.

Tested:
Testcase now runs and passes.

Signed-off-by: Matt Spinler <spinler@us.ibm.com>
Change-Id: I8cebbadc6061fd45fc6b3d6a33d0a4079f5de52d
diff --git a/presence/meson.build b/presence/meson.build
index e8f5476..1e728b9 100644
--- a/presence/meson.build
+++ b/presence/meson.build
@@ -47,3 +47,6 @@
     install: true,
 )
 
+if (get_option('tests').allowed())
+    subdir('test')
+endif