Fix encoding of padding bits to start with 0 bit

This patch is for fixing encoding of padding bits according to the
3gpp spec 44.060 section 11, wherein it shall always start with 0
bit followed with spare padding bits.

During introduction of basic EGPRS feature new hex dump messages
from a different working network log were used in Unit test. These
exposed the issue of incorrect handling of padding bits encoding
in osmo-pcu.

Corrections in the existing test vector of rlcmac is also updated.
In testsuite tbf appropriate corrections for the Tbftest.err is
also done.
diff --git a/tests/rlcmac/RLCMACTest.ok b/tests/rlcmac/RLCMACTest.ok
index 99117ff..0b4e154 100644
--- a/tests/rlcmac/RLCMACTest.ok
+++ b/tests/rlcmac/RLCMACTest.ok
@@ -7,13 +7,13 @@
 vector1 = 4e8250e3f1a81d882080b2b2b2b2b2b2b2b2b2b2b
 vector2 = 4e8250e3f1a81d882080b2b2b2b2b2b2b2b2b2b2b
 vector1 == vector2 : TRUE
-vector1 = 4828247a6a074227210b2b2b2b2b2b2b2b2b2b2b2b
+vector1 = 4828247a6a07422721032b2b2b2b2b2b2b2b2b2b2b
 =========Start DECODE===========
 +++++++++Finish DECODE++++++++++
 =========Start ENCODE=============
 +++++++++Finish ENCODE+++++++++++
-vector1 = 4828247a6a074227210b2b2b2b2b2b2b2b2b2b2b2b
-vector2 = 4828247a6a074227210b2b2b2b2b2b2b2b2b2b2b2b
+vector1 = 4828247a6a07422721032b2b2b2b2b2b2b2b2b2b2b
+vector2 = 4828247a6a07422721032b2b2b2b2b2b2b2b2b2b2b
 vector1 == vector2 : TRUE
 vector1 = 4724c040000000079eb2ac9402b2b2b2b2b2b
 =========Start DECODE===========
@@ -32,21 +32,21 @@
 vector2 = 47283c367513ba33304242b2b2b2b2b2b2b2b2b2b2b2b
 vector1 == vector2 : TRUE
  UPLINK 
-vector1 = 40e1e61d11f2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b
+vector1 = 40e1e61d11d2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b
 =========Start DECODE===========
 +++++++++Finish DECODE++++++++++
 =========Start ENCODE=============
 +++++++++Finish ENCODE+++++++++++
-vector1 = 40e1e61d11f2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b
-vector2 = 40e1e61d11f2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b
+vector1 = 40e1e61d11d2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b
+vector2 = 40e1e61d11d2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b
 vector1 == vector2 : TRUE
-vector1 = 40b802000000002480e0b2b2b2b2b2b2b2b2b
+vector1 = 40b802000000002480e032b2b2b2b2b2b2b2b
 =========Start DECODE===========
 +++++++++Finish DECODE++++++++++
 =========Start ENCODE=============
 +++++++++Finish ENCODE+++++++++++
-vector1 = 40b802000000002480e0b2b2b2b2b2b2b2b2b
-vector2 = 40b802000000002480e0b2b2b2b2b2b2b2b2b
+vector1 = 40b802000000002480e032b2b2b2b2b2b2b2b
+vector2 = 40b802000000002480e032b2b2b2b2b2b2b2b
 vector1 == vector2 : TRUE
 vector1 = 4016713dc09427ca2ae57ef90906aafc001f80222b
 =========Start DECODE===========