thirdparty/pjproject: fix deadlock in response retransmissions

The tdata containing the response can be shared by both the dialog
object and the tsx object.  In order to prevent the race condition
between the tsx retransmission and the dialog sending a response,
clone the tdata before modifying it for the dialog send response.

ASTERISK-27966 #close

Change-Id: Ic381004a3a212fe1d8eca0e707fe09dba4a6ab4e