index: Fix compiler warning

Problem:
----------------------------
index.c:420:18: warning: comparison of unsigned enum expression < 0 is
always false [-Wtautological-compare]
        if (type < 0 || type >= XATTROP_TYPE_END)
            ~~~~ ^ ~
1 warning generated.
----------------------------
Fix:
Add a -1 value in the enumeration and use that in if-statements.

Cherry picked from commit e221827c18ad4161a8e54ad67c9128ad234b8c03:
> BUG: 1335232
> Change-Id: I830a565b8d96d7b51ff775e94aa23dd567ffe0d9
> Signed-off-by: Niels de Vos <ndevos@redhat.com>
> Reviewed-on: http://review.gluster.org/14409
> Smoke: Gluster Build System <jenkins@build.gluster.com>
> Reviewed-by: Ravishankar N <ravishankar@redhat.com>
> CentOS-regression: Gluster Build System <jenkins@build.gluster.com>
> NetBSD-regression: NetBSD Build System <jenkins@build.gluster.org>
> Reviewed-by: Kaleb KEITHLEY <kkeithle@redhat.com>

The backport prevens the need for commit 137bd83 to be backported.
Commit e221827 undoes the ugly type-casting.

Change-Id: I65911a05de5f8b5634f1e8cf359c38dad7d125aa
BUG: 1336268
Signed-off-by: Ravishankar N <ravishankar@redhat.com>
Signed-off-by: Niels de Vos <ndevow@redhat.com>
Reviewed-on: http://review.gluster.org/14346
Tested-by: Niels de Vos <ndevos@redhat.com>
Smoke: Gluster Build System <jenkins@build.gluster.com>
NetBSD-regression: NetBSD Build System <jenkins@build.gluster.org>
CentOS-regression: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Kaleb KEITHLEY <kkeithle@redhat.com>

0 files changed, 0 insertions, 0 deletions