smoketest: pppoe-server: adjust client_ip_pool testcase to latest code fixes
smoketest: pppoe-server: adjust client_ip_pool testcase to latest code fixes

Commit 52ee92b8 ("pppoe: T3386: Fix client ip-pool stop range") fixed the
generated client range configuration line for Accel-PPP but missed out altering
the testcase, too which validates the generated configuration line.

vyos/vyos-1x,vyos/vyos-1x,vyos/vyos-1x,vyos/vyos-1x