EGL: add a missing native_window_api_disconnect

Add a native_window_api_disconnect for the case where
processAttributes() fails. Otherwise the next time this
function is called, it'll fail because native window is
still connected to the first API.

Test: NV internal regression tests including dEQP
Test: EGL_test --gtest_filter=EGLTest.EGLCreateWindowFailAndSucceed

Change-Id: I89712acf5ac40927e975357797a271c1bb680dbc
Merged-In: I89712acf5ac40927e975357797a271c1bb680dbc