evas: fix preload thread dead lock issue

evas: fix preload thread dead lock issue

    Summary:
    Add spin lock to access to new flag can check to
    status of the preload

    Reviewers: jpeg, cedric, jypark

    Subscribers: raster

    Differential Revision: https://phab.enlightenment.org/D3775

    Signed-off-by: Cedric Bail <cedric@osg.samsung.com>
    evas: fix preload thread deadlock issue

    Summary: Wrong condition makes deadlock issue.

    Reviewers: jpeg, jypark

    Subscribers: cedric

    Differential Revision: https://phab.enlightenment.org/D3742

    Signed-off-by: Cedric BAIL <cedric@osg.samsung.com>
Change-Id: I8fc9fa60c574c6dbfb6c3073925da867408cdb95