Handling of storage error dialog doesn't work

[jikortus]

The current handler for storage error dialog (displayed on the Welcome screen e. g. when two volume groups with identical names are found) doesn't work with current (RHEL-8+) dialog.

The text it looks for has changed, plus the reason of failure is not present in the heading, but in the error description.

What has to be done:

• Update the text in the heading of the dialg Anabot is looking for, don't use string formatting for RHEL-8+ to substitute the particular error as it's not present in the text anymore.
• Fix how the exact error (e. g. multiple LVM volume groups with the same name) is be checked, look for the text at the beginning of the error message text in the lower part of the dialog.