multi_usrp: Fix streamer destruction callback

The streamers were keeping a reference to the multi_usrp object, so the
object would not destruct when the user deleted or reset the shared
pointer to the object.  An error would occur if the user attempted to
make the same device and get streamers on it without explicitly deleting
the streamers first.

This change refactors the code such that the streamer destructor only
depends on the existence of a weak_ptr to the underlying rfnoc_graph
and a vector of edges returned by the connect function.  It checks to
see if the graph has been deleted before calling the functions to
disconnect the edges.  This allows the multi_usrp object and streamer
objects to be destructed in any order.

Signed-off-by: michael-west <michael.west@ettus.com>

0 files changed, 0 insertions, 0 deletions