debug/io-stats:fix compile warning

Compiler Warning:
---------------------------------------------------------
io-stats.c: In function 'io_stats_dump':
io-stats.c:950:24: warning: comparison between 'gf1_cli_stats_op' and
'enum gf1_cli_info_op' [-Wenum-compare]
                 if (op == GF_CLI_INFO_ALL ||
io-stats.c:951:24: warning: comparison between 'gf1_cli_stats_op' and
'enum gf1_cli_info_op' [-Wenum-compare]
                     op == GF_CLI_INFO_CUMULATIVE)
                        ^
---------------------------------------------------------
Fix: Use the appropriate enum in function defintion of io_stats_dump().
Note: Using the same BZ ID as the commit that introduced this argument.

Change-Id: I24e1aaf9ab86b4f337e3daa729d561ec208f2a95
BUG: 1030580
Signed-off-by: Ravishankar N <ravishankar@redhat.com>
Reviewed-on: http://review.gluster.org/7217
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>