supplicant: Tie P2P flush D-Bus call to the interface

As the callback for the call accesses GSupplicantInterface structure,
tie the pending call to the interface pointer so that it gets cancelled
if the interface is removed.

[connman] supplicant: Tie P2P flush D-Bus call to the interface
supplicant: rewrite pending DBus call handling for properties

Property-related D-Bus calls may be pending replies when the related
GSupplicantInterface structure is cleaned up. This results in an
attempt to access already freed memory when calls complete.

Fixed by keeping a list of pending property calls, and canceling the
calls related to an interface when the interface is removed. This is a
similar change to the one made earlier for pending method calls.

[connman] supplicant: rewrite pending DBus call handling for properties
wifi: cancel pending supplicant operations when removing

If there are pending D-Bus calls made inside supplicant code when
wifi_remove() frees the wifi struct, wifi plugin callback functions
may attempt to use already released memory when the calls complete.

Fixed by cancelling any outstanding supplicant calls in wifi_remove().

[connman] wifi: cancel pending supplicant operations when removing
Merge pull request #83 from hmallat/supplicant-dbus-call-cancellation

Supplicant dbus call cancellation