Change I22ff5a5a74527366da8f82982232d4e70e455570 changed
get_ha_sync_data_for_host such that if an agent requests a router's
details, then it is always returned, even when it doesn't have the key
'_ha_interface'. Further changes to this change tried to put this check
back in (Ie38baf061d678fc5d768195b25241efbad74e42f), but this patch
failed to do so for the case where no bindings were returned (possible
when the router has been concurrently deleted). This patch puts this
check back in.
Closes-Bug: #1607381
Change-Id: I047e53ea9b3e20a21051f29d0a44624e2a31c83c