Fixed improper use of readlink which does not add the trainling \0.

Adapted the unit test which did not simulate this behavior.

castor/tape/tapeserver/SCSI/Device.cpp

@@ -215,8 +215,10 @@ SCSI::DeviceInfo SCSI::DeviceVector::getDeviceInfo(const char * path) {
   {
     char rl[PATH_MAX];
     std::string lp = ret.sysfs_entry + "/generic";
-    if (-1 == m_sysWrapper.readlink(lp.c_str(), rl, sizeof (rl)))
+    ssize_t rlSize;
+    if (-1 == (rlSize = m_sysWrapper.readlink(lp.c_str(), rl, sizeof (rl) - 1)))
       throw exceptions::Errnum("Could not read link " + lp);
+    rl[rlSize] = '\0';
     std::string gl(rl);
     size_t pos = gl.find_last_of("/");
     if (pos == std::string::npos)

castor/tape/tapeserver/system/Wrapper.cpp

@@ -76,7 +76,11 @@ int System::fakeWrapper::readlink(const char* path, char* buf, size_t len) {
     return -1;
   }
   const std::string & link = m_links[std::string(path)];
-  strncpy(buf, link.c_str(), len);
+  /* Copy the link without the training \0 as it is the behavior 
+   of the real readlink */
+  size_t lenToCopy = link.size();
+  if (lenToCopy > len) lenToCopy = len;
+  link.copy(buf, lenToCopy);
   return len > link.size() ? link.size() : len;
 }