backport(autocomplete): Sync the zsh_autocomplete file with master

Some bug fixes have been added to master for the zsh_autocomplete function.
Backport this to make it available for v1 also.

Changelog: None

Signed-off-by: Ole Petter <ole.orhagen@northern.tech>

autocomplete/zsh_autocomplete

@@ -3,9 +3,19 @@
 _cli_zsh_autocomplete() {
 
   local -a opts
-  opts=("${(@f)$(_CLI_ZSH_AUTOCOMPLETE_HACK=1 ${words[@]:0:#words[@]-1} --generate-bash-completion)}")
+  local cur
+  cur=${words[-1]}
+  if [[ "$cur" == "-"* ]]; then
+    opts=("${(@f)$(_CLI_ZSH_AUTOCOMPLETE_HACK=1 ${words[@]:0:#words[@]-1} ${cur} --generate-bash-completion)}")
+  else
+    opts=("${(@f)$(_CLI_ZSH_AUTOCOMPLETE_HACK=1 ${words[@]:0:#words[@]-1} --generate-bash-completion)}")
+  fi
 
-  _describe 'values' opts
+  if [[ "${opts[1]}" != "" ]]; then
+    _describe 'values' opts
+  else
+    _files
+  fi
 
   return
 }