Allow profile's termainal size to work again

When Konsole Settings -> 'Use current window size on next startup' is
disabled, use the Profile's terminal size for new windows.

Many thanks to Roman Gilg (subdiff gmail com) for research and patch.

If there are no further issues, I'll commit to 15.12 branch (should go
.2 release).

REVIEW: 126924
CCBUG: 345403
(cherry picked from commit 55f02e5b)