classes/sstate: show progress during sstate object availability check
Show progress through bitbake's standard terminal UI when checking for
shared state object availability, since this can take some time if there
are a large number of tasks to be executed and/or the network connection
is slow.
Part of the implementation for [YOCTO #5853].
Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
