BuildSettingsWidget::createConfiguration() works with a BuildInfo
object borrowed from an IBuildConfigurationFactory, and uses it to create
a new build configuration.

The original BuildInfo object should not be permanently changed, as it's
only used here for creating the new build configuration.

Ideally, it should work on a clone of the buildinfo/factory, but that
would require adding and implementing a polymorphic clone method
for either class.

This commit works around this problem by restoring the original
displayName of the buildinfo after use.

Task-number: QTCREATORBUG-12955
Change-Id: Iccf2123c4377a39396860a1cfaa817a98dacebd4
Reviewed-by: Daniel Teske <daniel.teske@digia.com>