maintenance: Add missing limit parameters to some explode()

maintenance: Add missing limit parameters to some explode()

This is, in theory, a loophole that can not only cause such code to
consume suprising amounts of memory and runtime. It can also create
suprising results. For example, an input like

 -param="might contain a = char"

might result in a cut-off value.

Not so much of a problem in a maintenance script. But still good
practice, I find.

Change-Id: I14fb278e6fdb61d0c486ca7e23229851ea479408