Partially revert "mount: Check if src exists before mounted (ansible/ansible#61752)" (#33)

This reverts part of ansible commit 72023d7462e78635264fd12bfdb23894b4163cba.

The immediate reason is that it breaks mounts where src is not a path.
Examples of such mounts are network-based filesystems such as nfs, cifs,
glusterfs, ceph, virtual filesystems such as tmpfs or overlayfs, and
also UUID-based mounts. It is too hard to come with an exhaustive list,
especially if we take non-Linux systems into account, so don't even try.

Additionally, it did not really fix the issue (ansible/ansible#59183) that
it intended to fix, because the mount could fail but leave a non-working
fstab entry for reasons other than non-existing src path.

Restore fstab and remove the mount point after a failed mount

Add a reminder that not only devices can be mounted

Fixes: ansible/ansible#65855
Fixes: ansible/ansible#67588
Fixes: ansible/ansible#67966

Signed-off-by: Alexander E. Patrakov <patrakov@gmail.com>
Signed-off-by: Abhijeet Kasurde <akasurde@redhat.com>

Co-authored-by: Alexander E. Patrakov <patrakov@gmail.com>

tests/integration/targets/mount/aliases

@@ -2,4 +2,3 @@ needs/privileged
 needs/root
 shippable/posix/group1
 skip/aix
-disabled # fixme

tests/unit/modules/system/test_mount.py

@@ -2,9 +2,14 @@ import os
 import tempfile
 
 from ansible_collections.ansible.posix.tests.unit.compat import unittest
+from ansible_collections.ansible.posix.tests.unit.compat.mock import MagicMock
 from ansible.module_utils._text import to_bytes
 
-from ansible_collections.ansible.posix.plugins.modules.mount import get_linux_mounts
+from ansible_collections.ansible.posix.plugins.modules.mount import (
+    get_linux_mounts,
+    _set_mount_save_old,
+    set_mount,
+)
 
 
 class LinuxMountsTestCase(unittest.TestCase):
@@ -23,3 +28,32 @@ class LinuxMountsTestCase(unittest.TestCase):
         )
         mounts = get_linux_mounts(None, path)
         self.assertEqual(mounts['/tmp/bbb']['src'], '/tmp/aaa')
+
+    def test_set_mount_save_old(self):
+        module = MagicMock(name='AnsibleModule')
+        module.check_mode = True
+        module.params = {'backup': False}
+
+        fstab_data = [
+            'UUID=8ac075e3-1124-4bb6-bef7-a6811bf8b870 / xfs defaults 0 0\n',
+            '/swapfile none swap defaults 0 0\n'
+        ]
+        path = self._create_file("".join(fstab_data))
+        args = {
+            'fstab': path,
+            'name': '/data',
+            'src': '/dev/sdb1',
+            'fstype': 'ext4',
+            'opts': 'defaults',
+            'dump': '0',
+            'passno': '0',
+        }
+
+        name, changed = set_mount(module, args)
+        self.assertEqual(name, '/data')
+        self.assertTrue(changed)
+
+        name, backup_lines, changed = _set_mount_save_old(module, args)
+        self.assertEqual(backup_lines, fstab_data)
+        self.assertEqual(name, '/data')
+        self.assertTrue(changed)