xshared: do not lock again and again if "-w" option is not specified

After running the following commands, some confusing messages was printed
out:
  # while : ; do
  iptables -A INPUT &
  iptables -D INPUT &
  done
  [...]
  Another app is currently holding the xtables lock; still -9s 0us time
  ahead to have a chance to grab the lock...
  Another app is currently holding the xtables lock; still -29s 0us time
  ahead to have a chance to grab the lock...

If "-w" option is not specified, the "wait" will be zero, so we should
check whether the timer_left is less than wait_interval before we call
select to sleep.

Also remove unused "BASE_MICROSECONDS" and "struct timeval waited_time"
introduced by commit e8f857a5a151 ("xtables: Add an interval option for
xtables lock wait").

Fixes: e8f857a5a151 ("xtables: Add an interval option for xtables lock wait")
Signed-off-by: Liping Zhang <zlpnobody@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
(cherry picked from commit 24f8174646123c2833bc87967b366796231b04e0)

Bug: 36108349
Test: see top of change stack.
Change-Id: I54da3f5b1390f4e4cc20523575925aa2a428f39b
1 file changed