ipmi plugin: Improve error handling and handle a temporary error condition more grace...

ipmi plugin: Improve error handling and handle a temporary error condition more gracefully.

On a server IPMI readings suddenly failed causing the plugin to stop
collecting data.
The following entries got logged:

ipmi plugin: sensor_read_handler: Removing sensor Temp 7 processor (3.6), because it failed with status 0x10000d5.
ipmi plugin: sensor_read_handler: Removing sensor Temp 6 processor (3.5), because it failed with status 0x10000d5.
ipmi plugin: sensor_read_handler: Removing sensor Temp 5 power_supply (10.5), because it failed with status 0x10000d5.
ipmi plugin: sensor_read_handler: Removing sensor Temp 4 processor (3.4), because it failed with status 0x10000d5.
ipmi plugin: sensor_read_handler: Removing sensor Temp 3 processor (3.3), because it failed with status 0x10000d5.
ipmi plugin: sensor_read_handler: Removing sensor Temp 2 external_environment (39.1), because it failed with status 0x10000d5.
ipmi plugin: sensor_read_handler: Removing sensor Temp 1 system_internal_expansion_board (16.1), because it failed with status 0x10000d5.

This patch attempts to provide slightly better error message and just
skip current reading iteration if the error
IPMI_NOT_SUPPORTED_IN_PRESENT_STATE_CC is indicated.

This error happens e.g. when iLo firmware is upgraded (or reboots?) on
HP servers.