DTMF regression

```
What steps will reproduce the problem?

1. Checkout IMSDroid Revision 569 from SVN (at the time of this writing this is
the latest revision available)
2. Build it and run it on an Android device (In this case I've run it on a
Google Nexus 5 with Android 4.4.2 API 19)
3. Setup a SIP account. In my scenario everything is setup to work in the same
LAN network, so I don't have NAT or other things involved.
3. Call a number which has an IVR or does different actions based on the DTMF
tones received from the caller. In my scenario I've called *100 and the I've
sent 624# as DTMF tones.

What is the expected output? What do you see instead?

The DTMFs sent from the device are not recognized by the SIP server. I expect
the server to recognize them.

What version of the product are you using? On what operating system?

IMSDroid 2.569.1089 on Google Nexus 5 with Android 4.4.2 (API 19)

Please provide any additional information below.

When I do the same steps described above, but with IMSDroid 2.548.870 on the
same device, everything works as expected and the DTMF tones are correctly
detected by the SIP server. I run a freeswitch SIP server setup to work in
rfc2833 mode. I've done a dump with wireshark. One with IMSDroid 2.569.1089 and
one with IMSDroid 2.548.870, that you cand find attached to this issue.

```

Original issue reported on code.google.com by `alexgo...@gmail.com` on 30 May 2014 at 9:06

Attachments:
- [imsdroid_2.548.870.pcapng](https://storage.googleapis.com/google-code-attachments/imsdroid/issue-520/comment-0/imsdroid_2.548.870.pcapng)
- [imsdroid_2.569.1089.pcapng](https://storage.googleapis.com/google-code-attachments/imsdroid/issue-520/comment-0/imsdroid_2.569.1089.pcapng)