Set V_N and V_B to known initial state

Reset V_N and V_B in UL/DL window class constructors to make sure we
always start from known initial state.

Related: OS#1759
Change-Id: I8e14ffa913b49c5394229220de9165cdfaabdf19
Fixes: CID70468, CID70469.
diff --git a/src/rlc.h b/src/rlc.h
index fcc3edb..aac6b13 100644
--- a/src/rlc.h
+++ b/src/rlc.h
@@ -506,6 +506,7 @@
 	: m_v_s(0)
 	, m_v_a(0)
 {
+	reset();
 }
 
 inline const uint16_t gprs_rlc_dl_window::v_s() const
@@ -552,6 +553,7 @@
 	: m_v_r(0)
 	, m_v_q(0)
 {
+	m_v_n.reset();
 }
 
 inline bool gprs_rlc_ul_window::is_in_window(uint16_t bsn) const