keyfile_set_from_vardict: free the string array
keyfile_set_from_vardict: free the string array

g_variant_get_strv is (transfer container): the caller is expected to
free the array, but not the individual strings.

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