[M34-Merge] ewk_view_scale_get function shall behave like synchronous one

[M34-Merge] ewk_view_scale_get function shall behave like synchronous one

Although the ewk_view_scale_set is asynchronous, the TCT compliance tests
from webkit-efl EWK implementation require the getter to return the value
set by the setter even if the two functions were called immediately
after each other.
This change makes the setter modify the proxy value,
thereby subsequent calls of the getter will return proper value,
even if it hasn't been applied in the UI process.

Bug: http://107.108.218.239/bugzilla/show_bug.cgi?id=7679
Bug: http://107.108.218.239/bugzilla/show_bug.cgi?id=8260
Reviewed by: Antonio Gomes, SeungSeop Park

Change-Id: I34d1e77a97a0d7395538a6300b9430531f6934a7
Signed-off-by: Wojciech Bielawski <w.bielawski@samsung.com>