After reading in the database dump in the new install and starting the upgrade from 1.9.x to 2.0.2 the error

Table "upgrade_log" already exists

is shown with the following stack trace:

line 469 of /lib/ddl/database_manager.php: ddl_exception thrown
line 93 of /lib/db/upgrade.php: call to database_manager->create_table()
line 1383 of /lib/upgradelib.php: call to xmldb_main_upgrade()
line 252 of /admin/index.php: call to upgrade_core()

Based on what I found using Google, there seems to be no fix for the error and - since it is not possible to export courses from 1.9.x and import them into 2.0.x - either every course, etc. has to be created from scratch or the upgrade has to wait.