sanity: exclude boards for samples/net/test_15_4

Excluded Quark D2000, Nucleo F103RB, Olimexino STM32 for the
sample test_15_4. Boards doesn't have support for 15.4 neither
enough space.

JIRA: ZEP-738
Change-Id: I963509a77cdf6a8ff2efee2f2d4a498e3c07f9b5
Signed-off-by: Javier B Perez <javier.b.perez.hernandez@intel.com>