[lldb] Initialize reproducers in LocateSymbolFileTest
Since a842950b62b6d029a392c3c312c6495d6368c2a4 this test started using
the reproducer subsystem but we never initialized it in the test. The
Subsystem takes an argument, so we can't use the usual SubsystemRAII at the
moment to do this for us.
This just adds the initialize/terminate calls to get the test passing again.