segtree: Fix for last elem at interval end

segtree: Fix for last elem at interval end

Unclosed interval check at end of interval_map_decompose() missed to
check whether interval start is the last possible element in given set
before creating a range expression. This led to the last element
incorrectly printed as range from itself to itself. Fix this by
comparing the upper boundary against the lower one.

In order to keep indenting level low, invert the entry check and jump to
the end if it matches.

Signed-off-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>