test: signalqueue: add explicit cast to bool

React to a GCC7.2 behavioral differences where
assert(sdbusplus::message::message) no longer compiles.

sdbusplus::message::message implements operator bool which
prior to GCC7.2 was emitted implicitly.  Add an explicit
cast to bool where required.

Tested: Built repository using GCC 7.2
Change-Id: I49fb05d616ba1f790ef68365983b1f85aa91e46a
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
diff --git a/test/test.cpp b/test/test.cpp
index 849b60b..5d89f0d 100644
--- a/test/test.cpp
+++ b/test/test.cpp
@@ -244,7 +244,7 @@
         b.call(m);
 
         auto sig{queue.pop()};
-        assert(sig);
+        assert(static_cast<bool>(sig));
         sdbusplus::message::object_path signalPath;
         Object signalObjectType;
         sig.read(signalPath);
@@ -317,7 +317,7 @@
             {
                 std::vector<std::string> interfaces;
                 auto sig{queue.pop()};
-                assert(sig);
+                assert(static_cast<bool>(sig));
                 sig.read(sigpath);
                 assert(sigpath == deleteMeThree);
                 sig.read(interfaces);
@@ -386,7 +386,7 @@
             {
                 std::vector<std::string> interfaces;
                 auto sig{queue.pop()};
-                assert(sig);
+                assert(static_cast<bool>(sig));
                 sig.read(sigpath);
                 assert(sigpath == deleteMeOne);
                 sig.read(interfaces);
@@ -396,7 +396,7 @@
             {
                 std::vector<std::string> interfaces;
                 auto sig{queue.pop()};
-                assert(sig);
+                assert(static_cast<bool>(sig));
                 sig.read(sigpath);
                 assert(sigpath == deleteMeTwo);
                 sig.read(interfaces);
@@ -424,7 +424,7 @@
             {
                 std::vector<std::string> interfaces;
                 auto sig{queue.pop()};
-                assert(sig);
+                assert(static_cast<bool>(sig));
                 sig.read(sigpath);
                 assert(sigpath == deleteMeThree);
                 sig.read(interfaces);
@@ -498,14 +498,14 @@
             b.call(m);
             {
                 auto sig{queue.pop()};
-                assert(sig);
+                assert(static_cast<bool>(sig));
                 sig.read(signalPath);
                 assert(createMe1 == signalPath.str);
                 sig.read(signalObject);
             }
             {
                 auto sig{queue.pop()};
-                assert(sig);
+                assert(static_cast<bool>(sig));
                 sig.read(signalPath);
                 assert(createMe2 == signalPath.str);
                 sig.read(signalObject);