s4-test/tombstone_reanimation: Use TestCase.get_loadparm() to get lp context

Change-Id: I87c13b14c6e3d305342aaa24a1df43aeb69d348c
Signed-off-by: Kamen Mazdrashki <kamenim@samba.org>
s4-tests: Add tombstone_reanimation test case to s4 test suite

Change-Id: I84ff628496bfa3e0538011400328585d080f21b8
Signed-off-by: Kamen Mazdrashki <kamenim@samba.org>