samples/task_profile: fix testcase.ini's long lines

.ini format supports long lines by prefixing the continuation with an
empty line. Adding a backslash makes the backslash part of the value.

Change-Id: I0a1ade3a6bdf12281e61d06e21d7233d4b624b48
Signed-off-by: Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>