ANDROID: uid_sys_stats: Copy task_struct comm field to bigger buffer

get_task_comm() currently checks if buf_size != TASK_COMM_LEN
and fails even if sizeof(buf) > TASK_COMM_LEN.

Change-Id: Icb3e9c172607534ef1db10baf5d626083db73498
Signed-off-by: Dmitry Shmidt <dimitrysh@google.com>