bitbake: bb/ui: store_dependency_information optimization

bitbake: bb/ui: store_dependency_information optimization

This optimization is in support of the bug #5485. The function called
at the beginning of every build: store_dependency_information was taking
approximately 20sec and it was delaying the arrival of events from the
event queue. The change minimizes the calls to _save_a_task(),
reducing the time to half.

(Bitbake rev: b86fd2be40303d886fdb9ad3009355584d285acc)

Signed-off-by: Marius Avram <marius.avram@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>