make get_by_host use slave in periodic task

In periodic task functions nova prefer to use slave db
instead of primary db. This patch makes function
_get_host_volume_bdms to use slave db

Change-Id: Ia297524fc1acf06ab708509c805d14e215b10b86
Indicate whether service is down for mc driver

memcache driver for service didn't log any clue
whether the service is down or not. This patch add a
log to indicate it at DEBUG level.

Closes-Bug: #1382564

Change-Id: I05e12b56411f4475d1ef50e90e09abf75d7355b0
Only filter once for trusted filters

In spawn process the filters will be used only once if the
run_filter_once_per_request is set to True. This apply to the hosts
that will not be affected by previous instance resource consumption.
Trusted filter should be in this kind of filters.

Change-Id: Ia223797798679fecfcf90983ca81a9f395e67c3b
Network object: add missing translations

An exception was raised and not translated in commit
e134f81d85f42b87238f7786b0b50066129c968d.

Change-Id: I1c65041bd3a7152088f1660800d3a58f6fe12eea
Fixes multi-line strings with missing spaces

Multi-line concatenated strings are easily given bad spacing:

  "This looks like"
  "it will be OK"    => "This looks likeit will be OK"

This patch fixes those. I don't think it's possible to create
a hacking rule for this as any automated check will generate
too many false positives.

Change-Id: If89007f45d90ca5321336e3623139f9538ac06b8
Merge "Network object: add missing translations"
Merge "Indicate whether service is down for mc driver"
Merge "make get_by_host use slave in periodic task"
Merge "Only filter once for trusted filters"
Merge "Fixes multi-line strings with missing spaces"