Revert "Issue #1813832 by andypost, xjm, sun: Fixed Entity wrongly checks existence of ID in isNew() method."

This reverts commit 453b2517.

This broke testbot. Reverting temporarily.

Issue #1772584 by andypost, gumanist, nod_: Get rid of user_login_block() & user_login() in favour of user_login_form().

Issue #666412 by tayzlor, jaffaralia, iflista, mfb, xjm: Fixed Regression: RSS feed enclosure support lost from core.

Issue #1813832 by andypost, xjm, sun: Fixed Entity wrongly checks existence of ID in isNew() method.

Issue #1812822 by larowlan: Fixed field_test_entity_info() does not set a 'label' on the Test Entity.

Issue #1146244 by Dean Reilly, fago: Add tests for ensuring node is fully saved when hook_node_insert() fires.

Issue #1812170 by xjm, tim.plunkett: Remove dependency on the standard profile from LocaleContentTest.

Issue #1817484 by tomgeekery, kiamlaluno: Fixed The function contains a 'return' statement right at the end of the function.

Issue #1812732 by xjm: Use constants instead of integers in drupalCreateNode() and improve its documentation.

Issue #1782244 by heyrocker, andypost, tstoeckler: Convert image styles  array into ImageStyle (extends ConfigEntity).

Issue #1739928 by plach: Follow up for generalizing language configuration on content types to apply to terms and other entities.

Issue #1805996 by tim.plunkett: Add CHANGELOG.txt and MAINTAINERS.txt entries for Views and Views UI.