docker: update following name changes:

`backend_e2e` now print properly backend logs

docker/backend-dev/scripts/entrypoint.sh

@@ -0,0 +1,19 @@
+#!/bin/sh
+
+eval $(dbus-launch --sh-syntax)
+
+# default, backend is launched in foreground
+if [ $# -eq 0 ]
+then
+	exec libervia-backend fg
+fi
+
+# backend is launched with an explicit subcommand
+if [ $1 = fg -o $1 = bg -o $1 = debug -o $1 = stop -o $1 = status ]
+then
+	exec libervia-backend "$@"
+fi
+
+# a whole command is specified
+libervia-backend bg
+exec "$@"