Avoid to install a blank list of packages

There are some situations where the list of packages to install
in a image is blank (packages blacklisted) on opensuse based
distributions.

Change-Id: Ib720473fa63671ed974d41a86fe10a9b10720f5d
Optimizing directory creation.

Optimized the creation of directories by using the Brace expansion mechanism.

And corrected the dirname resolution to follow correct convention.

Change-Id: I048c04385d2706c4e38f8548555a59b0437e1fcd
Merge "Avoid to install a blank list of packages"
Merge "Optimizing directory creation."