container/init: configure interface lo

This enables loopback networking when owning the net namespace.

Signed-off-by: Ophestra <cat@gensokyo.uk>

container/container.go

@@ -263,6 +263,8 @@ func (p *Container) Start() error {
 			CAP_SYS_ADMIN,
 			// drop capabilities
 			CAP_SETPCAP,
+			// bring up loopback interface
+			CAP_NET_ADMIN,
 			// overlay access to upperdir and workdir
 			CAP_DAC_OVERRIDE,
 		},