CIFS: Improve DFS caching

[Tim Gardner]

SRU Justification

[Impact]

The Microsoft CIFS team is requesting to ensure these 5 patches are made available with 5.11 Azure tuned kernel

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/fs/cifs?id=6efa994e35a402ae4ae2161b6439c94b64816cee
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/fs/cifs?id=cdc3363065aba2711e51019b3d5787f044f8a133
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/fs/cifs?id=507345b5ae6a57b7ecd7550ff39282ed20de7b8d
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/fs/cifs?id=50630b3f1ada0bf412d3f28e73bac310448d9d6f
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/fs/cifs?id=506c1da44fee32ba1d3a70413289ad58c772bba6

[Test Plan]

Connect to a Windows DFS share

[Where problems could occur]

The CIFS connection could fail.

[Other Info]

https://canonical.my.salesforce.com/5004K000005r0uT

[Tim Gardner (timg-tpi)]

Test kernels at https://launchpad.net/~timg-tpi/+archive/ubuntu/cifs-dfs-cache-lp1937264