Permanently disables swap in securedrop-app-code preinst
Permanently disables swap in securedrop-app-code preinst

Checks for active swap on system, and if found:

  * disables it so the system won't write to it
  * shreds the contents so any sensitive data is destroyed

Regardless of whether an active swap config was disabled, any fstab
entry of type "swap" will be commented out, effectively disabling it
permanently by ensuring it won't be reenabled on subsequent reboots.

Closes #1620.

garrettr/securedrop,ehartsuyker/securedrop,garrettr/securedrop,micahflee/securedrop,conorsch/securedrop,heartsucker/securedrop,ehartsuyker/securedrop,ehartsuyker/securedrop,ageis/securedrop,ehartsuyker/securedrop,micahflee/securedrop,heartsucker/securedrop,ehartsuyker/securedrop,conorsch/securedrop,conorsch/securedrop,ageis/securedrop,heartsucker/securedrop,ehartsuyker/securedrop,ageis/securedrop,conorsch/securedrop,garrettr/securedrop,ageis/securedrop,garrettr/securedrop,heartsucker/securedrop,conorsch/securedrop,micahflee/securedrop,heartsucker/securedrop,micahflee/securedrop