Fix build against hidden Qt <5.15 deprecated API for stuff not covered on KDE CI
Building with -DWITH_NEW_SOLID_JOB=ON -DWITH_NEW_POWER_ASYNC_API=ON -DWITH_NEW_POWER_ASYNC_FREEDESKTOP=ON and also the HAL backend uncovered some more code which was using now hidden deprecated Qt API. Not covered on KDE CI (but first seen for the flags in in openSUSE package builds -> https://build.opensuse.org/package/show/KDE:Unstable:Frameworks/solid ).
Edited by Friedrich W. H. Kossebau