Remove deprecated is_method_error code

The is_method_error() function is no longer needed, instead a
try-catch block should be used instead.
Reference:
https://lists.ozlabs.org/pipermail/openbmc/2018-October/013696.html,

Change-Id: I1919ea33fc18be2b8afd51fb1f85ddef15041e7c
Signed-off-by: Adriana Kobylak <anoo@us.ibm.com>
diff --git a/activation.cpp b/activation.cpp
index a938b8b..73acc3d 100644
--- a/activation.cpp
+++ b/activation.cpp
@@ -205,9 +205,11 @@
     auto method = this->bus.new_method_call(VERSION_BUSNAME, path.c_str(),
                                             "xyz.openbmc_project.Object.Delete",
                                             "Delete");
-    auto mapperResponseMsg = bus.call(method);
-    // Check that the bus call didn't result in an error
-    if (mapperResponseMsg.is_method_error())
+    try
+    {
+        bus.call_noreply(method);
+    }
+    catch (const SdBusError& e)
     {
         log<level::ERR>("Error in Deleting image from image manager",
                         entry("VERSIONPATH=%s", path.c_str()));