Partial fix for bug#176140

[ancorgs]

Problem

The logic for adding _netdev needs to be refined... once again!

Now we have been told that _netdev should be skipped not only for "/" and all its subvolumes, but also for all the mount points that are based on the same disk than "/".

See https://bugzilla.suse.com/show_bug.cgi?id=1176140

Partial Solution

This expands the logic of #set_default_mount_options to honor the new proposed (and approved) logic described here:
https://gist.github.com/ancorgs/435328f6f16920a17b0b8cca7500526e#proposed-rspec-output-for-y2storagemountpoint

Unfortunately, this is only a solution if the root mount point is the first to be created. For example, imagine we create a mount point for "/var" in sda2. In that moment, #set_default_mount_options will add _netdev to it since there is no evidence of that partition being in the root disk. If at a later point, sda3 is created and mounted as "/", the mount options of sda2 will not be re-adjusted (so far, we have never needed to adjust the options of one mount point based on the presence of another one, so we have no such mechanism).

Testing

• Added a new unit test

Do not merge

We need a definitive solution.

[coveralls]

Coverage increased (+0.0005%) to 97.656% when pulling 6020362 on ancorgs:bug1176140_sp2 into ce6d89c on yast:SLE-15-SP2.

[dgdavid]

We need a definitive solution.

@ancorgs which is the status of this PR? Should we keep it open?

[ancorgs]

I guess this can be closed until we decide what the best mid-term solution is. I'm trying to re-activate the discussion here https://jira.suse.com/browse/PM-2830