MFC r248707:

hrStorageSize and hrStorageUsed are 32 bit integers, reporting a fs
size and usage in hrStorageAllocationUnits. If the file system has
more than 2^31 allocations it can not be shown correctly and the
meters are useless.

In such cases follow net-snmp behaviour and increase
hrStorageAllocationUnits so the values fit under INT_MAX.

PR:		bin/177183
Submitted by:	Eugene Grosbein egrosbein rdtc.ru