QA:Assign ext4 fs with mount point

= Description = | Assign ext4 fs with mount point

= How to test = |
 * 1) Prepare system with ext4 filesystem(s).
 * 2) Boot the installer.
 * 3) Select the ext4 filesystem as a mount point except of /boot, preferably some 'data' filesystem.
 * 4) Ensure installation is finished successfully.

= Expected Results = |
 * 1) ext4 filesystems are recognized.
 * 2) Mount point can be assigned to ext4 filesystem.
 * 3) Installation completes successfully.
 * 4) System starts properly with all filesystems mounted.