cardiff: Adding include_list in search_item

This feature will be used to search only a certain kind of item inside
the results.
cardiff: Naming discovered groups

When groups are created, let's number them to ease the identification
process.

A typical output looks like :

The 19 systems can be grouped in 3 groups of identical hardware
Group 0 (1 Systems)
-> CZ3404YWNW

Group 1 (15 Systems)
-> CZ3404YWP4, CZ3404YWP6, CZ3404YWPP, CZ3404YWP2, CZ3404YWPS,
CZ3404YWPX, CZ3404YWP8, CZ3404YWR0, CZ3404YWPE, CZ3404YWPA, CZ3404YWPC,
CZ3404YWPM, CZ3404YWPV, CZ3404YWPH, CZ3404YWPK

Group 2 (3 Systems)
-> CZ3404YWNN, CZ3404YWNT, CZ3404YWNR
cardiff: find_sub_element on a set of hosts

Adding a new parameter on find_sub_element that allow searching element
for a reduced set of hosts.
cardiff: Adding logical disk performance analysis

This patch add a processing of all disk performance to find the disks
that behave badly regarding the others.

First, we estimate for each testing mode if the grouped performance of the same disk (sda, sdb..) are coherent : If the standard deviation is more than 10% for sequential access, and 15% for random access of the average performance, it means that it's nearly impossible to find a bad system as all systems are behaving differently. The group is so reported as UNSTABLE.

If the group is coherent, we then analyze the performance of each disk of each host with the group. If the system is not between the average performance of the group modulo 2x the standard deviation, it means this disk seems over or under performing. The group performance is reported as SUSPICIOUS.

If all disks are in the group are performing in the same level of performance, the group is reported as CONSISTENT.

A typical output looks like :
Group 1 : Checking logical disks perf
standalone_randwrite_4k_IOps    : INFO    : sda : Group performance : min= 557.11, mean= 651.47, max= 745.83, stddev=  47.18
standalone_randwrite_4k_IOps    : WARNING : sda : CZ3404YWPP : Curious underperformance 514.00 : min_group = 557.11, mean_group = 651.47 max_group = 745.83
standalone_randwrite_4k_IOps    : WARNING : sda : Group performance : SUSPICIOUS
standalone_randwrite_4k_IOps    : INFO    : sdb : Group performance : min= 245.91, mean= 718.93, max=1191.96, stddev= 236.51
standalone_randwrite_4k_IOps    : ERROR   : sdb : Group's variance is too important :   32.90% of  718.93 whereas limit is set to 15.00%
standalone_randwrite_4k_IOps    : ERROR   : sdb : Group performance : UNSTABLE
standalone_randread_4k_IOps     : INFO    : sda : Group performance : min= 287.94, mean= 307.00, max= 326.06, stddev=   9.53
standalone_randread_4k_IOps     : INFO    : sda : Group performance : CONSISTENT
standalone_randread_4k_IOps     : INFO    : sdb : Group performance : min= 291.10, mean= 300.60, max= 310.10, stddev=   4.75
standalone_randread_4k_IOps     : WARNING : sdb : CZ3404YWPV : Curious underperformance 289.00 : min_group = 291.10, mean_group = 300.60 max_group = 310.10
standalone_randread_4k_IOps     : WARNING : sdb : Group performance : SUSPICIOUS
standalone_read_1M_IOps         : INFO    : sda : Group performance : min= 171.75, mean= 181.93, max= 192.12, stddev=   5.09
standalone_read_1M_IOps         : INFO    : sda : Group performance : CONSISTENT
standalone_read_1M_IOps         : INFO    : sdb : Group performance : min= 179.07, mean= 184.13, max= 189.20, stddev=   2.53
standalone_read_1M_IOps         : INFO    : sdb : Group performance : CONSISTENT
standalone_write_1M_IOps        : INFO    : sda : Group performance : min=   5.67, mean=   7.27, max=   8.86, stddev=   0.80
standalone_write_1M_IOps        : ERROR   : sda : Group's variance is too important :   10.99% of    7.27 whereas limit is set to 10.00%
standalone_write_1M_IOps        : ERROR   : sda : Group performance : UNSTABLE
standalone_write_1M_IOps        : INFO    : sdb : Group performance : min=   6.82, mean=   7.73, max=   8.65, stddev=   0.46
standalone_write_1M_IOps        : INFO    : sdb : Group performance : CONSISTENT
simultaneous_randwrite_4k_IOps  : INFO    : sda : Group performance : min= 236.85, mean= 760.13, max=1283.41, stddev= 261.64
simultaneous_randwrite_4k_IOps  : ERROR   : sda : Group's variance is too important :   34.42% of  760.13 whereas limit is set to 15.00%
simultaneous_randwrite_4k_IOps  : ERROR   : sda : Group performance : UNSTABLE
simultaneous_randwrite_4k_IOps  : INFO    : sdb : Group performance : min= 470.63, mean= 971.53, max=1472.43, stddev= 250.45
simultaneous_randwrite_4k_IOps  : ERROR   : sdb : Group's variance is too important :   25.78% of  971.53 whereas limit is set to 15.00%
simultaneous_randwrite_4k_IOps  : ERROR   : sdb : Group performance : UNSTABLE
simultaneous_randread_4k_IOps   : INFO    : sda : Group performance : min= 293.25, mean= 319.53, max= 345.82, stddev=  13.14
simultaneous_randread_4k_IOps   : WARNING : sda : CZ3404YWPX : Curious underperformance 287.00 : min_group = 293.25, mean_group = 319.53 max_group = 345.82
simultaneous_randread_4k_IOps   : WARNING : sda : Group performance : SUSPICIOUS
simultaneous_randread_4k_IOps   : INFO    : sdb : Group performance : min= 315.20, mean= 332.80, max= 350.40, stddev=   8.80
simultaneous_randread_4k_IOps   : WARNING : sdb : CZ3404YWPV : Curious underperformance 314.00 : min_group = 315.20, mean_group = 332.80 max_group = 350.40
simultaneous_randread_4k_IOps   : WARNING : sdb : Group performance : SUSPICIOUS
simultaneous_read_1M_IOps       : INFO    : sda : Group performance : min= 179.82, mean= 185.00, max= 190.18, stddev=   2.59
simultaneous_read_1M_IOps       : INFO    : sda : Group performance : CONSISTENT
simultaneous_read_1M_IOps       : INFO    : sdb : Group performance : min= 178.82, mean= 184.00, max= 189.18, stddev=   2.59
simultaneous_read_1M_IOps       : INFO    : sdb : Group performance : CONSISTENT
simultaneous_write_1M_IOps      : INFO    : sda : Group performance : min=  17.85, mean=  41.00, max=  64.15, stddev=  11.58
simultaneous_write_1M_IOps      : ERROR   : sda : Group's variance is too important :   28.23% of   41.00 whereas limit is set to 10.00%
simultaneous_write_1M_IOps      : ERROR   : sda : Group performance : UNSTABLE
simultaneous_write_1M_IOps      : INFO    : sdb : Group performance : min=  18.49, mean=  42.27, max=  66.05, stddev=  11.89
simultaneous_write_1M_IOps      : ERROR   : sdb : Group's variance is too important :   28.13% of   42.27 whereas limit is set to 10.00%
simultaneous_write_1M_IOps      : ERROR   : sdb : Group performance : UNSTABLE