reorder -icehouse branch limits

the -icehouse job branch limits were declared too late in the
layout.yaml causing them to have the unintended side effect of
making all -icehouse jobs voting (overriding earlier non-voting
stanzas).

move this to the top of the stack to ensure that we get the
behavior we were expecting.

Change-Id: I44ab42f2e405cc5c3e2cee5ba1f5afa85c39b8ee
Merge "reorder -icehouse branch limits"