apparmor: fix a memleak in free_ruleset()

When the aa_profile is released, we will call free_ruleset to
release aa_ruleset, but we don't free the memory of aa_ruleset,
so there will be memleak, fix it.

unreferenced object 0xffff8881475df800 (size 1024):
  comm "apparmor_parser", pid 883, jiffies 4294899650 (age 9114.088s)
  hex dump (first 32 bytes):
    00 f8 5d 47 81 88 ff ff 00 f8 5d 47 81 88 ff ff  ..]G......]G....
    00 00 00 00 00 00 00 00 00 dc 65 47 81 88 ff ff  ..........eG....
  backtrace:
    [<00000000370e658e>] __kmem_cache_alloc_node+0x182/0x700
    [<00000000f2f5a6d2>] kmalloc_trace+0x2c/0x130
    [<00000000c5c905b3>] aa_alloc_profile+0x1bc/0x5c0
    [<00000000bc4fa72b>] unpack_profile+0x319/0x30c0
    [<00000000eab791e9>] aa_unpack+0x307/0x1450
    [<000000002c3a6ee1>] aa_replace_profiles+0x1b8/0x3790
    [<00000000d0c3fd54>] policy_update+0x35a/0x890
    [<00000000d04fed90>] profile_replace+0x1d1/0x260
    [<00000000cba0c0a7>] vfs_write+0x283/0xd10
    [<000000006bae64a5>] ksys_write+0x134/0x260
    [<00000000b2fd8f31>] __x64_sys_write+0x78/0xb0
    [<00000000f3c8a015>] do_syscall_64+0x5c/0x90
    [<00000000a242b1db>] entry_SYSCALL_64_after_hwframe+0x63/0xcd

Fixes: 217af7e2 ("apparmor: refactor profile rules and attachments")
Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>