Don't leak rsector/sector in mp_label(..); use calloc instead of malloc + memset

[ngie]

Summary

Plug memory leaks in mp_label(..)

Don't leak rsector/sector in mp_label(..); use calloc instead of malloc + memset

MFC after: 1 week
Reported by: cppcheck
Sponsored by: EMC / Isilon Storage Division

Test Plan

% mdconfig -a -t malloc -s 25m
md0
% gmultipath label mpath md0
% gmultipath list
Geom name: mpath
Type: AUTOMATIC
Mode: Active/Passive
UUID: 21142ac6-9e1a-11e5-951e-000c29d8596e
State: DEGRADED
Providers:

1. Name: multipath/mpath Mediasize: 26213888 (25M) Sectorsize: 512 Mode: r0w0e0 State: DEGRADED

Consumers:

1. Name: md0 Mediasize: 26214400 (25M) Sectorsize: 512 Mode: r1w1e1 State: ACTIVE

% gmultipath add mpath md1
% gmultipath list
Geom name: mpath
Type: AUTOMATIC
Mode: Active/Passive
UUID: 21142ac6-9e1a-11e5-951e-000c29d8596e
State: OPTIMAL
Providers:

1. Name: multipath/mpath Mediasize: 26213888 (25M) Sectorsize: 512 Mode: r0w0e0 State: OPTIMAL

Consumers:

1. Name: md0 Mediasize: 26214400 (25M) Sectorsize: 512 Mode: r1w1e1 State: ACTIVE
2. Name: md1 Mediasize: 26214400 (25M) Sectorsize: 512 Mode: r1w1e1 State: PASSIVE

%

[mav]

I see no point in original NULL assignment. Other then that I have no objections.

[ngie]

In D4450#94151, @mav wrote:

I see no point in original NULL assignment. Other then that I have no objections.

Yeah, you're right. I'll remove them from the final diff.

Thanks!