Mount fixes

[patrakov]

SUMMARY

This is a resubmission of ansible/ansible#65869, which became necessary after splitting off the ansible.posix collection. Please apply ansible/ansible#68223 first.

The history is:

• a bug (mount module should fail when src doesn't exist when state is mounted ansible/ansible#59183) was reported that a broken fstab entry remains after a failed mount;
• an attempt to fix that bug was made by @Akasurde (mount: Check if src exists before mounted ansible/ansible#61752), but it completely broke mounting of network shares (Mount module fails on nfs mounts with "as it does not exist' ansible/ansible#65855 and Mount module not mounting sshfs using state: mounted ansible/ansible#67966), as well as UUID-based mounts (mount module cannot use UUID=... sources with mounted state ansible/ansible#67588), while still leaving cases (e.g. bad mount options) where a broken fstab entry remains on the system.

Therefore, this pull request reverts the bad fix and implements a hopefully better one, by letting the doomed mount fail and then dealing with the consequences (undoing the fstab line and directory creation).

In ansible/ansible#68102 @Akasurde confirmed that the bad fix needs to be reverted. In ansible/ansible#65869 there was a promise to test the new code, but so far it didn't materialize, and cannot materialize without ansible/ansible#68223.

ISSUE TYPE

• Bugfix Pull Request

COMPONENT NAME

mount

ADDITIONAL INFORMATION

See more discussion here: ansible/ansible#68155, ansible/ansible#68102, ansible/ansible#65544, ansible/ansible#65869.

Test cases:

# Should succeed assuming that /dev/sdb1 indeed contains xfs
ansible -i hosts myserver --become -m mount -a 'src=/dev/sdb1 path=/mnt/local state=mounted fstype=xfs'

# Should also work, was broken before the change
# "Unable to mount 192.168.0.1:/mnt/bigdisk as it does not exist"
ansible -i hosts myserver --become -m mount -a 'src=192.168.0.1:/mnt/bigdisk path=/mnt/big state=mounted fstype=nfs'

# Should fail without changing /etc/fstab and without leaving /mnt/bad
ansible -i hosts myserver --become -m mount -a 'src=/dev/sdb1 path=/mnt/bad state=mounted fstype=ext4'

[gundalow]

@patrakov Thank you for this PR.
At the moment the integration tests for mount aren't working, so we will hold off merging this PR.
Just leaving a negative review to avoid it being accidentally merged

[Akasurde]

@patrakov Thanks for the contribution. I merged these changes with additional test via #33. Closing this. Thanks.