fixed install template path

spells/menu/bitcoin/bitcoin-menu

@@ -26,7 +26,8 @@ display_menu() {
 	      menu "$title" "$set_config" "$change_directory" "$clear_cache" "$repair_permissions" "$bitcoin_server_option" "$install_service_option" "$install_bitcoin_option" "$exit_option"
 	    fi
     else
-    	install_service_option="Install Bitcoin Service%install-service-template ./bitcoin.service \"BITCOIND=`which bitcoind`\""
+    	script_dir=$(cd -P -- "$(dirname -- "$0")" && pwd -P)
+    	install_service_option="Install Bitcoin Service%install-service-template $script_dir/bitcoin.service \"BITCOIND=`which bitcoind`\""
     	menu "$title" "$set_config" "$change_directory" "$clear_cache" "$repair_permissions" "$install_service_option" "$install_bitcoin_option" "$exit_option"
 	fi
   else