lldpcli: Add support to set iface-pattern

This patch adds a new configure lldp command to set iface-pattern

Currently only sets iface-pattern on the server.
More incremental work is needed to trigger an interface
update and send.

Signed-off-by: Roopa Prabhu <roopa@cumulusnetworks.com>
lldpctl.h: document possibility to write iface-pattern
lldpcli: document "configure lldp iface-pattern" in manual page
lib: fix a memory leak when modifying interface pattern
client: trigger interface refresh when updating interface pattern
ctl: fix a memory leak when cleaning control socket
client: fix a memory leak when changing lldpd configuration

lldpd_config_cleanup() does not free the configuration structure.