LU-1644 ptlrpc: fix return type of boolean functions

LU-1644 ptlrpc: fix return type of boolean functions

Some functions are returning type int with values 0 or 1 when
they could be returning bool.  Fix up the return type of:

    lustre_req_swabbed()
    lustre_rep_swabbed()
    ptlrpc_req_need_swab()
    ptlrpc_rep_need_swab()
    ptlrpc_buf_need_swab()

Test-Parameters: trivial
Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Change-Id: I758afbf2d50ee9c0930d3080016803a299ecab07
Reviewed-on: https://review.whamcloud.com/32088
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>