After signing a generic message, the device does not return to the home screen

**Describe the bug**
After asking the device to sign a generic msg (in the JS library is done by calling `devSkycoinSignMessage`) and confirming the operation, the device screen shows `Signature success` and the message stays there until another operation is done. The problem is that the user would expect the device to return to the home screen, as that is the behavior after doing any other operation. As the behavior after signing the msg is not standar, the user could try to close the message pressing the buttons or think that the device stoped working.

Note: it is not planned to allow to sign generic messages soon, so this issue is not for V1.

**Environment information:**

- OS: Windows
- Platform: X64
- Firmware Version: ffd6fcd

**Steps to Reproduce**
Call the function for signing a generic msg (in the JS library is done by calling `devSkycoinSignMessage`) and accept the operation in the device.

**Actual behavior**
After finishing the operation, de device will show `Signature success` instead of the home screen. The msg can not be closed by pressing the device buttons.

**Expected behavior**
The device should return to the home screen.

**Additional context**
As this is the only function that does not return to the home screen after finishing, the behavior could confuse the users.

**Possible implementation**