[FIX] Svace issues

[FIX] Svace issues

-----------------------------------------------------
| WGID  | Type                      | File          |
|----------------------------------------------------
| 24915 | NEGATIVE_CODE_ERROR       | da_protocol.c |
| 25135 | TOCTTOU_SEQUENCE          | da_protocol.c |
| 25452 | DEREF_AFTER_NULL          | da_protocol.c |
| 25453 | DEREF_AFTER_NULL          | da_protocol.c |
| 26296 | SIGNED_TO_BIGGER_UNDIGNED | sys_stat.c    |
| 26856 | NOCAST.INTEGER_OVERFLOW   | sys_stat.c    |
|----------------------------------------------------

Change-Id: I08d791b3fb592b1f56d7ecf8ad853f7f423bb2a8
Signed-off-by: Vitaliy Cherepanov <v.cherepanov@samsung.com>