tc: Add flow control setting on PRIO qdisc

* Enable filter fw, qdiscs prio, and qdisc fifo.
* Add "flow enable|disable" clause for PRIO qdisc
* Now using sanitized kernel headers

CRs-fixed: 665103
Change-Id: I7ccfe9717bf21738c66b33dbafe04b2c3a3a912a
iproute2: lib: fix crash seen while running tc q_htb with rate specified

While running tc q_htb with rate specified, a crash is seen.
signal 11 (SIGSEGV), code 2 (SEGV_ACCERR)
The exact location of the crash is get_hz() where the extern int
is assigned the value from the function __get_hz().
The current suspicion is that the issue could be because of the
declaration of the variable util.h and for some reason the definition
in util.c is not being read. Explictly assigning a value to this
variable seems to be allocating the memory and no crash is seen.

CRs-fixed: 665103
Change-Id: Ia6c1d7f33978f7831b662109eb211fe771c59a14