Allow SMBDiagnostics and NfsDiagnostics scripts to specify trace point capture size to given value

Current script limit the trace capture size to kernel buffer size, but if we want to run capture traces for longer duration (if we dont know when issue gets hit and if system has large disk size) then we should have option to specify the size of trace points to safe value.

https://github.com/Azure-Samples/azure-files-samples/tree/master/SMBDiagnostics
https://github.com/Azure-Samples/azure-files-samples/tree/master/NfsDiagnostics