combobox: fix continuous clicks on hover

combobox: fix continuous clicks on hover

Summary:
Continouous clicks on hover would need to ensure that variable
on_dismiss of combobox_vertical style in hover.edc should 0 when slot is being shown, otherwise events
would be disabled on hover even though swallow content is shown.

@fix

Signed-off-by: Divyesh Purohit <purohit.div@gmail.com>
Test Plan:
Click continouosly on combobox and events on hover would be
disabled.

Reviewers: cedric

Differential Revision: https://phab.enlightenment.org/D3601

Signed-off-by: Cedric BAIL <cedric@osg.samsung.com>