Update alliancecan.md

[pvandyken]

Updated the instructions for getting sshfs working, as I thought it could use more specificity

[kaitj]

If you're updating this, would you mind also making a change to the settings for handling MFA? These were based on the combination of some discussion with Alliance support and also the following: https://docs.alliancecan.ca/wiki/Multifactor_authentication#Configuring_your_SSH_client_to_only_ask_every_so_often

• Add the following to .ssh/config such that MFA is only asked after a period of time rather than each time ssh/sshfs is called:

  Host HOSTNAME
  ControlPath ~/.ssh/cm-%r@%h:%p
  ControlMaster auto
  ControlPersist 10m # Can change this to 0 to only ask once

• Update sshfs with the following options (removes ServerAliveCount and updates ServerAliveInterval):

reconnect,ServerAliveInterval=0,Compression=no,follow_symlinks

The second point was at least working on a cloud instance I was testing this out on. To that end, the second point is more just to let the mount persist, else sshfs will always ask about MFA (and doesn't actually take config AFAIK into consideration).

Note these were all on Linux distros, so not sure of the equivalent for Windows.

[pvandyken]

@kaitj, gonna save that point for a new PR