Turn off debug logging in sqlalchemy by default

This commit adds a new config option sqlalchemy_debug which is used
for enabling debug messages from sqlalchemy. Previously, this logging
was enabled whenever debug was enabled. The debug log level for
sqlalchemy prints out all SQL queries and results which is way too
verbose for most cases where just debug logging is useful. This
change disables this previous behavior by defaulting the new option
to false and decoupling it from the debug config option.

DocImpact

Change-Id: I298c40b71ed0b8772ff956f61f8d94217bce0e11
Stub out dependency on subprocess in unit tests

Stub out the sheepdog Store dependency on subprocess communication
with collie.  This results in many unnecessary pipes being created
on POSIX systems.

For unit testing purposes, do not create the sheepdog store.  (There
are no unit tests for this functionality anyway.)

Change-Id: I54014a502891ae52bb567f3fae32e6ff0c74332a
Add unit test for migration 010

This continues implementing unit tests for the migrations that are
currently missing them

Change-Id: I461f133c6dc5a9dcc775cc71571e1acfd746d9ee
Merge "Turn off debug logging in sqlalchemy by default"
Merge "Stub out dependency on subprocess in unit tests"
ambiguous column 'checksum' error when querying image-list(v2).

- removed ambiguity by prefixing the column with models.Image
- based on the image_get_all() method logic, changed the
filters.get(checksum) to filters.pop(checksum) to
avoid multiple addition of same criteria in the where clause.
- modified the functional db test to include this failing scenario.

Fixes bug 1205330

Change-Id: Ic2b5b9bed7c02865d66e2f92846dcc9c0e7e2f97
Merge "Add unit test for migration 010"
Merge "ambiguous column 'checksum' error when querying image-list(v2)."