multibuttonentry: Fix MBE item box min size calc error.

multibuttonentry: Fix MBE item box min size calc error.

Summary:
Before item packed again in mbe box. box calc own min height.
In this case, there is no need to increase line number when  entry is box item.
Actually the min height of box calculated wrong here.

@fix

Test Plan:
Give a color to internal box.
Then items add.
Check the internal box area got a wrong height value.

Reviewers: Hermet, cedric

Differential Revision: https://phab.enlightenment.org/D3102