tests/rlcmac: Add test to showcase that decode_gsm_ra_cap() fails

Currently code using that function in osmo-pcu is disabled, allegadly
because SGSN was sending incorrect values, but it looks more like a CSN1
issue.

Related: OS#1525, OS#3499
Change-Id: I92c86397f988afaa791871d823a45fa85054f3bb
diff --git a/tests/rlcmac/RLCMACTest.ok b/tests/rlcmac/RLCMACTest.ok
index 2af4d90..5793d57 100644
--- a/tests/rlcmac/RLCMACTest.ok
+++ b/tests/rlcmac/RLCMACTest.ok
@@ -123,3 +123,5 @@
 vector2 = 40 0a 90 20 00 00 00 00 00 00 00 30 10 01 2a 08 00 13 2b 2b 2b 2b 2b 
 vector1 == vector2 : TRUE
 *** testCsnLeftAlignedVarBmpBounds ***
+*** testRAcap ***
+decode_gsm_ra_cap fails? yes