Prevent Duplicate Inlet Segments

If one WELSEGS keyword does not redefine every existing segment,
then we risk adding the same inlet segment multiple times.  If that
happens, we get a segment structure for which there might appear to
be multiple inlet segments on the same branch which is not possible
in a tree structure.  This commit prevents that situation by only
adding the new segment number if it is not already listed in
'm_inlet_segments'.

src/opm/input/eclipse/Schedule/MSW/Segment.cpp

@@ -24,9 +24,11 @@
 #include <opm/input/eclipse/Schedule/MSW/SICD.hpp>
 #include <opm/input/eclipse/Schedule/MSW/Valve.hpp>
 
+#include <algorithm>
 #include <cassert>
 #include <stdexcept>
 #include <string>
+#include <vector>
 
 namespace {
 
@@ -277,8 +279,15 @@ namespace Opm {
         return m_inlet_segments;
     }
 
-    void Segment::addInletSegment(const int segment_number_in) {
-        m_inlet_segments.push_back(segment_number_in);
+    void Segment::addInletSegment(const int segment_number_in)
+    {
+        auto segPos = std::find(this->m_inlet_segments.begin(),
+                                this->m_inlet_segments.end(),
+                                segment_number_in);
+
+        if (segPos == this->m_inlet_segments.end()) {
+            this->m_inlet_segments.push_back(segment_number_in);
+        }
     }
 
     double Segment::invalidValue() {