porting: `pidof` portability for OSX/FreeBSD

- Provide a portable `pidof` just to be used specifically with
  glusterfs regression tests on OSX and FreeBSD. This was
  written after countless hrs of effort to get a sane `pidof`
  working on either of the environments.
  `pidof` comes at the wake of lack of proper procfs support
  and also incompatible way of handling process names since
  glusterd/glusterfs are symbolic links to 'glusterfsd'
- tests/utils/* directory should be part of 'PATH' to avoid
  abspath calculation using $(dirname)
- cleanup() - rpcinfo command prints error on FreeBSD/OSX fix it

Change-Id: I35f86273624cb279da1c8fae056ca27669e251d8
BUG: 1131713
Signed-off-by: Harshavardhana <harsha@harshavardhana.net>
Reviewed-on: http://review.gluster.org/8499
Reviewed-by: Jeff Darcy <jdarcy@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>