src/sock.c: compile fix
src/sock.c: compile fix

When trying to compile code using gcc 5.1.1, the wollowing warning
occurs:

src/util.c: In function ‘spawn_sock_wait’:
src/util.c:281:5: error: type of ‘sk’ defaults to ‘int’
[-Werror=implicit-int]
 int spawn_sock_wait(sk)
     ^
cc1: all warnings being treated as errors

Fix it.

Signed-off-by: Kir Kolyshkin <c0159612b0ef32139322233232df1a0d189c4b9b@openvz.org>

xemul/libct,avagin/libct,xemul/libct,avagin/libct,hallyn/libct,xemul/libct,hallyn/libct,avagin/libct,xemul/libct,hallyn/libct