_ostree_sysroot_write_deployments_internal: stop leaking hash table
_ostree_sysroot_write_deployments_internal: stop leaking hash table

It appears the result of assign_bootserials() is never actually used,
but I haven't changed it to return void right now.

Leak found with valgrind memcheck.

Signed-off-by: Simon McVittie <smcv@debian.org>

Closes: #556
Approved by: cgwalters

GNOME/ostree,GNOME/ostree,GNOME/ostree,GNOME/ostree,GNOME/ostree