CLOUDSTACK-8999: Don't override resource if provided by agent.properties

If a custom resource (kvm/libvirt implementation) is defined in agent.properties
don't override with the default, but check and fallback to the default if
resource property not defined

Signed-off-by: Rohit Yadav <rohit.yadav@shapeblue.com>
(cherry picked from commit 536a8b2)
Signed-off-by: Rohit Yadav <rohit.yadav@shapeblue.com>

Author: yadvr

python/lib/cloudutils/serviceConfig.py

@@ -678,7 +678,8 @@ def configAgent(self):
             cfo.addEntry("guid", str(self.syscfg.env.uuid))
             if cfo.getEntry("local.storage.uuid") == "":
                 cfo.addEntry("local.storage.uuid", str(bash("uuidgen").getStdout()))
-            cfo.addEntry("resource", "com.cloud.hypervisor.kvm.resource.LibvirtComputingResource")
+            if cfo.getEntry("resource") == "":
+                cfo.addEntry("resource", "com.cloud.hypervisor.kvm.resource.LibvirtComputingResource")
             cfo.save()
 
             self.syscfg.svo.stopService("cloudstack-agent")