[PATCH 0/1][SRU][Trusty/Utopic/Vivid/Wily](upstream) xfrm: dst_entries_init() per-net dst_ops

[Dan Streetman]

Patch cherry-picked from upstream commit
a8a572a6b5f2a79280d6e302cb3c1cb1fbaeb3e8 with only minor context
changes needed to Trusty/Utopic.

This fixes an error in counting dst objects when using ipsec with
multiple net namespaces; without this, one (or more) namespaces' dst
count will incorrectly increase until it reaches the limit, at which
point its ipsec network is no longer usable.

User tested against lts-vivid kernel only; I tested all 3 others manually.