Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>

This patch switch the old switch-based cache req code to
the new plugin-based.

Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>

This patch adds all existing functionality into plugins.

Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>

cache_req grown quite big from the original code and it turned out
that using switch statements to branch code for different cases
makes the code quite hard to read and further extend and any
modification to the logic itself is difficult.

This patch changes the switch statements to plugins with small
functions and separates logic into multiple modules. This gives
us better control over the code and improves readability and
maintainability while keeping code duplication to minimum.

Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>
Reviewed-by: Petr Cech <pcech@redhat.com>

Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>

Dlopen test was added to blacklist due to following reason:
> Disable running dlopen-tests under Valgrind as their use of dlclose
> makes Valgrind drop symbols and produce meaningless backtraces, which
> cannot be matched with specific suppressions.

It's true that dlclose makes meaningless backtraces but backtraces should
not be generated otherwise there is a bug in some library which need to be
fixed and not suppressed.

Reviewed-by: Nikolai Kondrashov <Nikolai.Kondrashov@redhat.com>

The current code checks only for "HAVE_PYTHON_BINDINGS", which is not
even a valid check. Let's do the proper check according to the python
version (HAVE_PYTHON2_BINDINGS or HAVE_PYTHON3_BINDINGS).

Signed-off-by: Fabiano Fidêncio <fidencio@redhat.com>
Reviewed-by: Lukáš Slebodník <lslebodn@redhat.com>