Adds MySQL as an option for integration specs.

To use MySQL, specify DB=mysql in your environment. Any other value will
cause Postgres to be used.

Unquotes double quotes in apply spec string, as MySQL stores them
quoted, or at the adapter renders the string with escaped quotes in the
tasks list. Postgres doesn't show this behavior, so not unescaping broke
our integration tests.

Signed-off-by: Matthew Boedicker <mboedicker@pivotallabs.com>
Stemcell spec assets should specify version in stemcell.MF as a string, not an integer
cli: stemcell: add --skip-if-exists option to upload stemcell command

Conflicts:
	cli/lib/cli/commands/stemcell.rb

Conflicts:
	bosh_cli/lib/cli/commands/stemcell.rb

Conflicts:
	bosh_cli/lib/cli/commands/stemcell.rb

Conflicts:
	bosh_cli/spec/unit/deployment_helper_spec.rb
Add support for —skip-if-exists flag for remote stemcell uploads, and provide integration test coverage

[#65126256]
Remove unused private method in cli/stemcell
Backfill unit tests for cli/stemcell/upload when stemcell is remote and --skip-if-exists flag is given

[finishes #65126256]