Operation symbol of the MPLS label.
If the symbol is range(5), the objects h3cAclLinkL2LabelRangeBegin and
h3cAclLinkL2LabelRangeEnd should have different values indicating a range.
Otherwise, only h3cAclLinkL2LabelRangeBegin counts,
object h3cAclLinkL2LabelRangeEnd is ignored.
invalid(0) -- unavailable
lt(1) -- less than
eq(2) -- equal
gt(3) -- great than
neq(4) -- not equal
range(5) -- a range with two ends included