nsk/monitoring: ThreadMXBean fails. getThreadAllocatedBytes() return value is not sufficiently accurate

The following test failures were spotted in the 2014-08-27 RT_Baseline nightly:

nsk/monitoring/ThreadMXBean/GetThreadAllocatedBytes/doubleAllocationTest_directly_class

    This test failed due to "nsk.share.TestFailure: Failure! Expected
    getThreadAllocatedBytes() measurement for some thread at one
    moment could not be greater then similar measurement for the
    same thread at later moment. Thread allocates same amount of
    memory before each measurement. Excpected ~2 times difference.
    Recieved: 122920 and 290808"

nsk/monitoring/ThreadMXBean/GetThreadAllocatedBytes/doubleAllocationTest_proxy_default_class

    This test failed due to "nsk.share.TestFailure: Failure! Expected
    getThreadAllocatedBytes() measurement for some thread at one
    moment could not be greater then similar measurement for the
    same thread at later moment. Thread allocates same amount of
    memory before each measurement. Excpected ~2 times difference.
    Recieved: 123192 and 291384

nsk/monitoring/ThreadMXBean/GetThreadAllocatedBytes/doubleAllocationTest_server_custom_class

    This test failed due to "nsk.share.TestFailure: Failure! Expected
     getThreadAllocatedBytes() measurement for some thread at one
     moment could not be greater then similar measurement for the
     same thread at later moment. Thread allocates same amount of
     memory before each measurement. Excpected ~2 times difference.
     Recieved: 123320 and 290952

RULE nsk/monitoring/ThreadMXBean/GetThreadAllocatedBytes/doubleAllocationTest_directly_class Exception nsk.share.TestFailure: Failure! Expected getThreadAllocatedBytes() measurement for some thread at one moment could not be greater then similar measurement for the same thread at later moment. Thread allocates same amount of memory before each measurement. Excpected ~2 times difference. Recieved: ... and ...

RULE nsk/monitoring/ThreadMXBean/GetThreadAllocatedBytes/doubleAllocationTest_proxy_default_class Exception nsk.share.TestFailure: Failure! Expected getThreadAllocatedBytes() measurement for some thread at one moment could not be greater then similar measurement for the same thread at later moment. Thread allocates same amount of memory before each measurement. Excpected ~2 times difference. Recieved: ... and ...

RULE nsk/monitoring/ThreadMXBean/GetThreadAllocatedBytes/doubleAllocationTest_server_custom_class Exception nsk.share.TestFailure: Failure! Expected getThreadAllocatedBytes() measurement for some thread at one moment could not be greater then similar measurement for the same thread at later moment. Thread allocates same amount of memory before each measurement. Excpected ~2 times difference. Recieved: ... and ...