session: Add more debugging logs
session: Add more debugging logs

Initial SPICE connection can sometimes fail without clear indications
where/how it failed. This commit adds more debug logs/more accurate logs
in order to help narrow down such issues.

guodong/spice-gtk,elmarco/spice-gtk,elmarco/spice-gtk,Fantu/spice-gtk,elmarco/spice-gtk,Fantu/spice-gtk,SPICE/spice-gtk,guodong/spice-gtk,SPICE/spice-gtk,flexVDI/spice-gtk,flexVDI/spice-gtk,freedesktop-unofficial-mirror/spice__spice-gtk,guodong/spice-gtk,elmarco/spice-gtk,freedesktop-unofficial-mirror/spice__spice-gtk,SPICE/spice-gtk,fgouget/spice-gtk,guodong/spice-gtk,Fantu/spice-gtk,Fantu/spice-gtk,fgouget/spice-gtk,freedesktop-unofficial-mirror/spice__spice-gtk,freedesktop-unofficial-mirror/spice__spice-gtk,SPICE/spice-gtk,fgouget/spice-gtk