Adding respond code/body check for successful command execution

modules/exploits/linux/http/imperva_securesphere_exec.rb

@@ -98,8 +98,14 @@ class MetasploitModule < Msf::Exploit::Remote
     rescue Rex::ConnectionError, Errno::ENOTCONN => e
       fail_with(Failure::Unreachable, "#{peer} - Could not connect to the web service")
     end
-    if res && res.code == 401
-      fail_with(Failure::NoAccess, 'Authorization Failure, valid agent registration credential is required')
+    if res
+      if res.code == 401
+        fail_with(Failure::NoAccess, 'Authorization Failure, valid agent registration credential is required')
+      end
+
+      unless res.code == 406 and res.body.include?("impctl")
+        fail_with(Failure::Unknown, 'Server did not respond in an expected way')
+      end
     end
     res
   end