commons: use long to store updates count of a gauge

to prevent integer overflow

Ticket: #8158
Acked-by: Gerd Behrmann
Target: master
Require-book: no
Require-notes: no
(cherry picked from commit d5512f62eec2ab040df0bbd87e1280c68594ac1f)
Signed-off-by: Tigran Mkrtchyan <tigran.mkrtchyan@desy.de>
Merge pull request #351 from kofemann/fix-counters-2.6

commons: use long to store updates count of a gauge