Upgrade issue 8.1.9.2 -> 9.1

[anon30676603]

As explained in your github issue we have a FAQ here explaining the needed steps:

Updates between multiple major versions and downgrades are unsupported

Problem: A "updates between multiple major versions and downgrades are unsupported" message is shown during an update/upgrade Description: As the message is telling you, you have done an unsupported upgrade path. For example: Original version: 8.0.2 Upgraded version: 8.2.6 In this case you have skipped the 8.1.x major upgrade which is unsupported as stated within the documentation. In order to find out between which versions your are stuck, check the following files in the ownCloud fol…