staging: lustre: ptlrpc: return a meaningful status from ptlrpcd_init()

This patch has the following:
1) Fix for the return value from ptlrpcd_init(). It will now return a
   correct status instead of returning zero always.
2) ptlrpcd_addref() should not increment ptlrpcd_users on error.
3) Added code in a mdc_setup() and mgc_setup() to test the return
   value of ptlrpcd_addref() and return on error.

Signed-off-by: Swapnil Pimpale <spimpale@ddn.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-3808
Reviewed-on: http://review.whamcloud.com/7522


Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>