config: fix one-node dumpconfig, add dm_config_write_one_node
A regression introduced in 2.02.89 (
11e520256b3005ed813ce83f8770aaab74edef3f)
caused the lvm dumpconfig <node> to print out
the node as well as its subsequent siblings.
The information about "only_one" mode got lost.
Before this patch (just an example node):
# lvm dumpconfig global/use_lvmetad
use_lvmetad=1
thin_check_executable="/usr/sbin/thin_check"
thin_check_options="-q"
(...all nodes to the end of the section)
With this patch applied:
# lvm dumpconfig global/use_lvmetad
use_lvmetad=1