Eliminate duplicate entries from list_active_containers (v2)

Eliminate duplicate entries from list_active_containers (v2)

list_active_containers parses /proc/net/unix which can contain multiple entries for the same container;

0000000000000000: 00000002 00000000 00010000 0001 01 273672 @/var/lib/lxc/6/command
0000000000000000: 00000002 00000000 00010000 0001 01 274395 @/var/lib/lxc/5/command
0000000000000000: 00000002 00000000 00010000 0001 01 273890 @/var/lib/lxc/4/command
0000000000000000: 00000002 00000000 00010000 0001 01 273141 @/var/lib/lxc/3/command
0000000000000000: 00000002 00000000 00010000 0001 01 273915 @/var/lib/lxc/2/command
0000000000000000: 00000002 00000000 00010000 0001 01 273683 @/var/lib/lxc/1/command
0000000000000000: 00000002 00000000 00010000 0001 01 273074 @/var/lib/lxc/0/command
0000000000000000: 00000002 00000000 00010000 0001 01 273931 @/var/lib/lxc/9/command
0000000000000000: 00000002 00000000 00010000 0001 01 273110 @/var/lib/lxc/8/command
0000000000000000: 00000002 00000000 00010000 0001 01 273390 @/var/lib/lxc/7/command
0000000000000000: 00000003 00000000 00000000 0001 03 275903 @/var/lib/lxc/8/command
0000000000000000: 00000003 00000000 00000000 0001 03 276043 @/var/lib/lxc/1/command
0000000000000000: 00000003 00000000 00000000 0001 03 273301 @/var/lib/lxc/0/command
0000000000000000: 00000003 00000000 00000000 0001 03 275650 @/var/lib/lxc/4/command

On this system list_active_containers returns 14 containers while only 10 containers are running.

Following patch;

	* Introduces array_contains function to do a binary search on given array,
	* Starts to sort arrays inside the add_to_clist and add_to_names functions,
	* Consumes array_contains in list_active_containers to eliminate duplicates,
	* Replaces the linear search code in lxcapi_get_interfaces with the new function.

Changes since v1:
	* Do not load containers if a if a container list is not passed in
	* Fix possible memory leaks in lxcapi_get_ips and lxcapi_get_interfaces if realloc fails

Signed-off-by: S.Çağlar Onur <caglar@10ur.org>
Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>