Fix exit status codes

Using an exit status of -1 everywhere leads to the status being
converted to 255 when output to a calling application. While this does
signify an error it has a reserved meaning for exit status out of range.
Lets use a valid general exit status of 1 instead.

Change-Id: I326701c78985e34c430c258fe31d9e910da10405
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/monitor/main.cpp b/monitor/main.cpp
index 84dd7d1..512e3f7 100644
--- a/monitor/main.cpp
+++ b/monitor/main.cpp
@@ -35,7 +35,7 @@
     if (argc != 2)
     {
         args.usage(argv);
-        exit(-1);
+        return 1;
     }
 
     Mode mode;
@@ -50,7 +50,7 @@
     else
     {
         args.usage(argv);
-        exit(-1);
+        return 1;
     }
 
     auto r = sd_event_default(&events);
@@ -58,7 +58,7 @@
     {
         log<level::ERR>("Failed call to sd_event_default()",
                         entry("ERROR=%s", strerror(-r)));
-        return -1;
+        return 1;
     }
 
     std::unique_ptr<phosphor::fan::trust::Manager> trust =
@@ -101,5 +101,5 @@
         }
     }
 
-    return -1;
+    return 1;
 }