test: unit test fixes for vtable exception

Seeing the following unit test failures due to duplicate
objects being put onto the dbus.  This is likely due to a
change in an underlying library to be more stringent.  Changed
the object path for the second objects to avoid the exception.

[ RUN      ] TestSNMPClient.CheckPersistency
unknown file: Failure
C++ exception with description "sd_bus_add_object_vtable:
org.freedesktop.DBus.Error.FileExists: File exists" thrown in the test body.
[  FAILED  ] TestSNMPClient.CheckPersistency (0 ms)

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I16f06cc1249ebc2c6957b8429141ba0d02b05fb9
2 files changed