Allocate sdp_origin members using `str_init_dup_str()`
which uses g_malloc, so that when freeing the sdp_origin
structure later in `sdp_orig_free()` it doesn't inadvertently
lead to the seg fault.
Otherwise if any member isn't recovered (e.g. username)
it remains pointing to NULL with 0 len, which will be gracefully
handled in `str_free_dup()`.
Change-Id: I131f0096103052445754cc01ac5072776e957cda
(cherry picked from commit 94c26e92b5)
Donat Zenichev