files: fix inh leak in inherit_fd_add

coverity CID 389190:

1538int inherit_fd_add(int fd, char *key)
1539{
1540        struct inherit_fd *inh;
...
    2. alloc_fn: Storage is returned from allocation function malloc.
    3. var_assign: Assigning: ___p = storage returned from malloc(32UL).
    4. Condition !___p, taking false branch.
    5. leaked_storage: Variable ___p going out of scope leaks the storage it points to.
    6. var_assign: Assigning: inh = ({...; ___p;}).
1548        inh = xmalloc(sizeof *inh);
    7. Condition inh == NULL, taking false branch.
1549        if (inh == NULL)
1550                return -1;
1551
...
    9. Condition !___p, taking true branch.
1555        inh->inh_id = xstrdup(key);
    10. Condition inh->inh_id == NULL, taking true branch.
1556        if (inh->inh_id == NULL)
    CID 389190 (#1 of 1): Resource leak (RESOURCE_LEAK)11. leaked_storage: Variable inh going out of scope leaks the storage it points to.
1557                return -1;

We should free inh on inh_id allocation error path in inherit_fd_add.

Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>

criu/files.c

@@ -1553,8 +1553,10 @@ int inherit_fd_add(int fd, char *key)
 		inh_fd_max = fd;
 
 	inh->inh_id = xstrdup(key);
-	if (inh->inh_id == NULL)
+	if (inh->inh_id == NULL) {
+		xfree(inh);
 		return -1;
+	}
 
 	inh->inh_fd = fd;
 	list_add_tail(&inh->inh_list, &opts.inherit_fds);