add kmod.is_loaded to check if a kernel module is currently loaded.

this
  if salt['kmod.is_loaded']('aacraid')

now obsoletes my workaround:
  if salt['cmd.retcode']('lsmod |grep ^aacraid') == 0

in sls files
Merge pull request #5783 from pille/kmod-is_loaded

add kmod.is_loaded to check if a kernel module is currently loaded.