Veto the first pulse in LoadEventPreNexus

[mantid-builder]

This issue was originally TRAC 4652

Original Reporter: @jzikovsky

Marie tells me that the first pulse of data at SNS is always bad, and so should be rejected from LoadEventPreNexus

Note: is this from this run cycle or all the time?

[mantid-builder]

@NickDraper (2012-04-30T14:12:57):
Moved at end of release 2.1

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@NickDraper (2012-08-10T12:43:38):
Moved at the end of release 2.2

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@NickDraper (2012-10-28T11:38:50):
Moved to milestone 2.4

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@NickDraper (2013-04-29T09:49:39):
Moved to r2.6 at the end of r2.5

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@NickDraper (2013-07-26T13:54:59):
Moved to backlog at the code freeze for R2.6

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@NickDraper (2014-02-14T11:04:56):
Bulk move to assigned at the introduction of the triage step

[peterfpeterson]

We are not generally concerned with preNeXus files