Installer: [FIX] skip test if test file is no symlink
Installer: [FIX] skip test if test file is no symlink

Precondition::Image tests need symlinks to work. Module::Install
breaks symlinks so skip tests unless test files are still
symlinks. Skip check was for a special ENV variable before
which makes less sense.

tapper/Tapper-Installer,tapper/Tapper-Installer