daemon: Enable debugging for the main daemon by GVFS_DEBUG
daemon: Enable debugging for the main daemon by GVFS_DEBUG

This is currently more-or-less just a cosmetic issue, because there aren't
any debug prints in the main daemon, and because other daemons are
spawned with the same enviroment. However this fixes debugging for the
proposed admin daemon, because GVFS_DEBUG environment variable is not
passed in pkexec environment.

gicmo/gvfs,gicmo/gvfs,gicmo/gvfs,gicmo/gvfs