libcli:security:sddl: accept only 8-4-4-4-12 GUIDs

libcli:security:sddl: accept only 8-4-4-4-12 GUIDs

Before we would take strings in a variety of lengths and formats,
which is not what Windows does or [MS-DTYP] says.

This was found by looking at evolved fuzz seeds. Note the 16 and 32
byte sequences in GUID position below:

$ hd $(ls -t seeds/fuzz_sddl_parse/* | head -1)| head
00000000  44 3a 41 52 50 50 50 50  50 28 4f 4c 3b 3b 46 57  |D:ARPPPPP(OL;;FW|
00000010  3b 30 7e ff ff ff ff ff  ff ff 2d 31 38 f5 ff ff  |;0~.......-18...|
00000020  fb 3b 3b 52 43 29 28 4f  44 3b 3b 46 57 3b 3b 3b  |.;;RC)(OD;;FW;;;|
00000030  52 43 29 28 4f 44 3b 3b  46 57 3b 30 30 ff ff ff  |RC)(OD;;FW;00...|
00000040  fb 30 e9 9b 3c cf e6 f5  ff ff fb 3b 3b 52 43 29  |.0..<......;;RC)|
00000050  28 4f 44 3b 3b 46 57 43  52 3b 3b 3b 52 43 29 28  |(OD;;FWCR;;;RC)(|
00000060  4f 44 3b 3b 46 58 47 52  3b 3b 33 43 43 35 38 37  |OD;;FXGR;;3CC587|
00000070  32 35 44 44 44 44 44 44  44 44 44 44 44 44 44 44  |25DDDDDDDDDDDDDD|
00000080  44 44 44 44 44 44 44 44  44 44 3b 52 43 29 28 4f  |DDDDDDDDDD;RC)(O|
00000090  44 3b 3b 46 58 3b 3b 3b  52 43 29 28 4f 44 3b 3b  |D;;FX;;;RC)(OD;;|

Signed-off-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>