move the part of code for fetch transient_for in eval time to _e_shell_surface_parent...

move the part of code for fetch transient_for in eval time to _e_shell_surface_parent_set().

Summary:
we need to set ec->parent before eval time.
that's because client can request to commit surface calling shell.configure() before eval time.
in this case, ec->parent isn't set yet, configure(move) will be failed.

in order to fix it, we have to set ec->parent in _e_shell_surface_parent_set() before eval time,
but we should check if ec already have parent, and if so, remove its parent's transients before change the value of ec->parent.

Test Plan: N/A

Reviewers: devilhorns

Subscribers: cedric

Differential Revision: https://phab.enlightenment.org/D1177