fix: bug in apt module when python-apt is not available

##### Issue Type: Bug Fix Pull request
##### Ansible Version: devel >= 1.5.3
##### Environment: from Debian 7 managing Debian 7
##### Summary:

When python-apt is not installed the apt module tries to use apt-get, update apt-cache and install python-apt. But due to pull request #5222 modifications and use of the unsafe string '&&' the proper command was never executed.

This fix is minimal and uses the use_unsafe_shell=True parameter to make it finally work.
Any input appreciated, 

Regards, 

@Spiroid & @Ssaboum