Fix processes resource user and command truncation

[alexpop]

Fixes #995

Uses code submitted by @Anirudh-Gupta here: #1173

Linux:

inspec> processes('/opt/chef-compliance/embedded/service/core/bin/core run').list
=> [#<struct Inspec::Resources::Processes::Process
  label="system_u:system_r:init_t:s0",
  pid=801,
  cpu="0.0",
  mem="3.7",
  vsz=481740,
  rss=57368,
  tty="?",
  stat="Ssl",
  start="12:43:15",
  time="00:00:02",
  user="chef-compliance",
  command=
   "/opt/chef-compliance/embedded/service/core/bin/core run --mode=setup --oidc --oidc-issuer-url https://ap-cc6.opschef.tv --oidc-client-id JZik-QcuP1LK2lOmL8l1qQwyazeI6XoUhvYnOb7oFz0=@ap-cc6.opschef.tv --oidc-redirect-url https://ap-cc6.opschef.tv/api/callback">]

OSX:

inspec> processes('Support/mdworker -s mdworker').list
=> [#<struct Inspec::Resources::Processes::Process
  label=nil,
  pid=92252,
  cpu="0.0",
  mem="0.1",
  vsz=2519384,
  rss=12628,
  tty="??",
  stat="S",
  start="3:03PM",
  time="0:00.03",
  user="_spotlight",
  command=
   "/System/Library/Frameworks/CoreServices.framework/Frameworks/Metadata.framework/Versions/A/Support/mdworker -s mdworker -c MDSImporterWorker -m com.apple.mdworker.shared">]

[Anirudh-Gupta]

Just to add to it - Limiting the user field here since Usernames may only be upto 32 chars long. (Taken from man page - https://linux.die.net/man/8/useradd)
Can also use args instead of command. Both can be used interchangeably.