Remember the flag suppressing special char handling

TESTED:
- Manually type "123#"
-> Should cause special-char-sequence handling

- Have Intent with "tel:123%23"
-> Should *not* cause the handling

- Try other USSD sequences
-> Should behave similarly as above

- Force config change after having the Intent
-> Should *not* cause the handling

- Remove and add '#' after having the Intent
-> Should cause the handling assuming the user explicitly requested
   to do so.

- Try other USSD sequences
-> Should behave similarly as shown above

Bug: 6726923
Change-Id: Ie62a448675ac558ecdeea43da01082712edee35a