Stop overriding CONF.default_log_levels per binary

Overriding CONF.default_log_levels means we loose some explicitly set
default values such as 'iso8601=WARN'. Also explicitly overriding
CONF.default_log_levels means that default_log_levels cannot be set in a
config file.

Change-Id: Ib5103b88ec3f9ccd9d516032c6a13dc2fa4bcb5e
Fix H201 violations and re-enable gating

H201 got stricter in hacking 0.9, so fix new violations and
re-enable gating.

Change-Id: Ie79b04bc1ae2d4784318c19661584d02b7bee088
Implements: blueprint reduce-flake8-ignore-rules
Fix early resource property value validation

Currently resource property validation fails if resource it
depends on is not created.

This change skips a property constraint validation if its intrinsic
function resolution does not find the dependant resource.

Change-Id: I2056c89437e8df2a59726b60c3c12f19f713d84d
Partial-Bug: #1317636
Make sure we can create an empty template

The initial bug was for HOT, but this fixes the same issue
in CFN too.

1) all calls to template[section] should return {} and not
   None by default (hot was correct, but not cfn)
2) the validate needs to access the raw template "self.t" so
   make sure we have a similar logic there too.
3) when warning for zero resources, look for len(resoruces) == 0 not
   None.

Change-Id: Iee6e2abbf13173c17d92f47b8a7efe207c29a984
Closes-bug: #1339893
Pass user_creds_id when creating backup stack

When creating a backup stack on update, we don't want to create a
new user_creds record, or update won't work with a trust-scoped
token.  So instead pass the existing stack user_creds_id in to the
constructor when creating the backup stack.

The current behavior is actually doubly wrong, since we don't delete
user_creds records when deleting the backup stack, so the stale
creds records are probably left behind in the DB.

Change-Id: I6bd0568fdf5301b876c40acddc73542bcfc224e3
Partial-Bug: #1342593
Merge "Make sure we can create an empty template"
Merge "Fix H201 violations and re-enable gating"
Merge "Fix early resource property value validation"
Merge "Pass user_creds_id when creating backup stack"
Merge "Stop overriding CONF.default_log_levels per binary"