ipacm: add mechanism to cache ct events

1) Current logic is to get the conntrack dump first time when tethering
is enabled.
2) Once we have the conntrack handles, add mechanism to cache CT events
when upstream is not set.
3) Also make changes to reset the socket receive timeout to 0 so that
nfct_catch doesn't return EAGAIN. And add check to retry when we receive
EILSEQ.

Change-Id: I37877c19f11abd3fdb9f7f6c96933a592e6a1490
4 files changed
tree: 906eeeffc77e69904e425056911a601cbe7dd0be
  1. hal/
  2. ipacm/
  3. ipanat/
  4. configure.ac
  5. ipacm_vendor_product.mk
  6. Makefile.am