ssh connection plugin: Report missing sudo password

If no password is provided, sudo hangs at the prompt. Identify this and
report that the password is missing as an error.
VPC security group membership fix for boto.

* facts now provides a list of existing vpc security group memberships
* adding a comma separated list of sg-* tags properly modifies membership
module replace - report changed only if contents is changed
Fix race conditions where a process gets in state "Running"
between the restart/start command and the summary command.

Refactor to avoid repeating the status, and fail if a given call to monit fails.
Only update submodules when recursive is true
Adds support for VPC subnets to ELB
module docker_image - default tag latest

Fix constant rebuild of image if no tag specified.
Fix for https://github.com/ansible/ansible/issues/7054 - when renaming an instance and waiting for the change to occur, force result.id to the name of the new instance so the subsequent call to get_current_resource succeeds.
Fix #7057 missing False default for vars_prompt

The test for default should be "is not None" since a boolean value of
False is a valid value.

See discussion at:
  https://groups.google.com/forum/#!topic/ansible-project/oc1_zE-FnyI
Adding support for purging subnets
module docker - add docker version comment

Default docker version 0.9.1 from Ubuntu 14.04 LTS don't report APIVersion.
Updated and corrected example section
Use empty string rather than None to avoid TypeError
Improve error messages.
Ensure the validation string has %s in it
made enabled/disabled checks of apache2_module workable
Fix sync_binlog name in mysql_variables example

The previous sync_binary_log is not a real MySQL variable.
Merge branch 'fixing_apache2_module' of https://github.com/berendt/ansible into berendt-fixing_apache2_module
Merge pull request #7294 from adamchainz/patch-1

Fix sync_binlog name in mysql_variables example
Make sure distro variable is set if python-apt is installed

Fixes #7295
[get_url] check against lowered stripped sha256sum

The content of the sha256sum attribute should be lowered before comparing it with the calculated sha256sum.

In the following example the used sha256sum uses ABC.. and not abc.. and the check failed. This should not happen.

```
TASK: [get_url url=http://ftp.fau.de/apache/hadoop/common/hadoop-2.4.0/hadoop-2.4.0.tar.gz dest=/home/vagrant/hadoop-2.4.0.tar.gz mode=0644 sha256sum=024326AC68A1A68B5566B10F95609EAAFD9F70CFEB37FCA0E97CBB1674E57C3A] ***
failed: [instance000] => {"failed": true}
msg: The SHA-256 checksum for /home/vagrant/hadoop-2.4.0.tar.gz did not match 024326AC68A1A68B5566B10F95609EAAFD9F70CFEB37FCA0E97CBB1674E57C3A; it was 024326ac68a1a68b5566b10f95609eaafd9f70cfeb37fca0e97cbb1674e57c3a.

FATAL: all hosts have already failed -- aborting
```