Storage snmp/wmi mislabeled volumes on Windows

Windows volumes have an extra backslash when polled via SNMP, and an incorrect rrd filename when polled via WMI. This causes issues with historic data when changing methods.

Windows responds to host-resources-mib while polling via snmp, however, net-snmp output containing backslashes is escaped with an extra backslash. This patch removes the extra backslash from $descr so that paths are correct in the web interface, database, and rrd files. Existing Windows volumes should be removed or have both storage.storage_descr updated and rrd file renamed.

It also uses the correct storage_mib as referenced in the database for rrd filenames. WMI output returns paths correctly, but rrd filenames contain hrstorage instead of host-resources-mib as stored in storage.storage_mib. This is noted in OBSERVIUM-938.

Last, unknown volumes are skipped and device rediscovery is requested.

Before:

storage-host-resources-mib-C____Label___Serial_Number_9a842de8.rrd

storage-hrstorage-C___Label___Serial_Number_9a842de8.rrd

C:\\

After:

storage-host-resources-mib-C___Label___Serial_Number_9a842de8.rrd

C:\