Regression test portability: rpc-coverage

- pull include.rc when running rpc-coverage.sh to get BSD stat(1)
  compatibility.
- fix type in statfs_test and use mode instead of size so that
  it cannot pass by chance like it did.
- BSD tail does not support --pid; Avoid that option by making
  the test simplier.
- Use a subshell instead of pushd/popd, which seems more reliable.
- Use flock -x instead of flock -e: same result on Linux, compatible
  with NetBSD flock.
- when using file descriptors in the shell, avoit too high numbers
  otherwise we can easily hit the descriptor limit.

BUG: 1129939
Change-Id: I51bad02a0ef47f20e4a2c49098c1c6701b7e6b09
Signed-off-by: Emmanuel Dreyfus <manu@netbsd.org>
Reviewed-on: http://review.gluster.org/8566
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Kaleb KEITHLEY <kkeithle@redhat.com>
Reviewed-by: Harshavardhana <harsha@harshavardhana.net>
Tested-by: Harshavardhana <harsha@harshavardhana.net>