usb-dbg: remove is_method_error call

An `is_method_error` is not appropriate after an sdbus `call` since
`call` will always throw an exception.  Remove the pointless call
and instead catch the exception.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I8f4f1f3b257e7a0e8d54eb96273504455d611857
diff --git a/src/usb-dbg.cpp b/src/usb-dbg.cpp
index 57c3339..f02469e 100644
--- a/src/usb-dbg.cpp
+++ b/src/usb-dbg.cpp
@@ -556,20 +556,23 @@
                                        "org.openbmc.Ipmb", "sendRequest");
     method.append(bicAddr, netFn, lun, cmd, cmdData);
 
-    auto reply = bus->call(method);
-    if (reply.is_method_error())
+    try
+    {
+        auto reply = bus->call(method);
+
+        IpmbMethodType resp;
+        reply.read(resp);
+
+        respData = std::move(
+            std::get<std::remove_reference_t<decltype(respData)>>(resp));
+    }
+    catch (const sdbusplus::exception_t& e)
     {
         phosphor::logging::log<phosphor::logging::level::ERR>(
             "Error reading from BIC");
         return -1;
     }
 
-    IpmbMethodType resp;
-    reply.read(resp);
-
-    respData =
-        std::move(std::get<std::remove_reference_t<decltype(respData)>>(resp));
-
     return 0;
 }
 
@@ -594,20 +597,23 @@
                                        "org.openbmc.Ipmb", "sendRequest");
     method.append(meAddress, netFn, lun, cmd, cmdData);
 
-    auto reply = bus->call(method);
-    if (reply.is_method_error())
+    try
+    {
+        auto reply = bus->call(method);
+
+        IpmbMethodType resp;
+        reply.read(resp);
+
+        respData = std::move(
+            std::get<std::remove_reference_t<decltype(respData)>>(resp));
+    }
+    catch (const sdbusplus::exception_t& e)
     {
         phosphor::logging::log<phosphor::logging::level::ERR>(
             "Error reading from ME");
         return -1;
     }
 
-    IpmbMethodType resp;
-    reply.read(resp);
-
-    respData =
-        std::move(std::get<std::remove_reference_t<decltype(respData)>>(resp));
-
     if (DEBUG)
     {
         std::cout << "ME resp data: ";