Bug 1531: Check for packages

Bug 1531: Check for packages

Fixes logic to check for packages.  Originally based on dpkg -l, which could
return packages that were once installed, then removed.  Instead a new function
has been created that takes a list of packages to check and uses dpkg -L, which
will return an error if a package is not, or no longer, installed

Fixes bug 1531

Change-Id: Ie6a92a4211a0ec0ecc5b3d08166dad6c5d3a1134
Signed-off-by: beierlm <mark.beierl@canonical.com>
Signed-off-by: garciadeblas <gerardo.garciadeblas@telefonica.com>