Remove hacks in ConfigService for older Poco versions

Older versions of Poco didn't have an AbstractConfiguration::remove member
so we had to fake it. This is no longer required as we need the newer
versions due to other bug fixes.
Refs #11871

Code/Mantid/Framework/Kernel/inc/MantidKernel/ConfigService.h

@@ -326,8 +326,6 @@ class MANTID_KERNEL_DLL ConfigServiceImpl {
 
   /// The list of available facilities
   std::vector<FacilityInfo *> m_facilities;
-  /// Define a flag value for a removed property
-  const std::string m_removedFlag;
 
   /// local cache of proxy details
   Kernel::ProxyInfo m_proxyInfo;

Code/Mantid/Framework/Kernel/src/ConfigService.cpp

@@ -149,7 +149,7 @@ ConfigServiceImpl::ConfigServiceImpl()
       m_user_properties_file_name("Mantid.user.properties"),
 #endif
       m_DataSearchDirs(), m_UserSearchDirs(), m_InstrumentDirs(),
-      m_instr_prefixes(), m_removedFlag("@@REMOVED@@"), m_proxyInfo(),
+      m_instr_prefixes(), m_proxyInfo(),
       m_isProxySet(false) {
   // getting at system details
   m_pSysConfig = new WrappedObject<Poco::Util::SystemConfiguration>;
@@ -943,8 +943,6 @@ std::string ConfigServiceImpl::getString(const std::string &keyName,
   std::string retVal;
   try {
     retVal = m_pConf->getString(keyName);
-    if (retVal == m_removedFlag)
-      retVal = "";
   }
   catch (Poco::NotFoundException &) {
     g_log.debug() << "Unable to find " << keyName << " in the properties file"
@@ -966,30 +964,8 @@ std::string ConfigServiceImpl::getString(const std::string &keyName,
 std::vector<std::string>
 ConfigServiceImpl::getKeys(const std::string &keyName) const {
   std::vector<std::string> rawKeys;
-  std::vector<std::string> keyVector;
-  keyVector.reserve(rawKeys.size());
-  try {
-    m_pConf->keys(keyName, rawKeys);
-    // Work around a limitation of Poco < v1.4 which has no remove functionality
-    // so check those that have been marked with the correct flag
-    const size_t nraw = rawKeys.size();
-    for (size_t i = 0; i < nraw; ++i) {
-      const std::string key = rawKeys[i];
-      try {
-        if (m_pConf->getString(key) == m_removedFlag)
-          continue;
-      }
-      catch (Poco::NotFoundException &) {
-      }
-      keyVector.push_back(key);
-    }
-  }
-  catch (Poco::NotFoundException &) {
-    g_log.debug() << "Unable to find " << keyName << " in the properties file"
-                  << std::endl;
-    keyVector.clear();
-  }
-  return keyVector;
+  m_pConf->keys(keyName, rawKeys);
+  return rawKeys;
 }
 
 /**
@@ -1039,16 +1015,7 @@ std::vector<std::string> ConfigServiceImpl::keys() const {
  *  @param rootName :: The key that is to be deleted
  */
 void ConfigServiceImpl::remove(const std::string &rootName) const {
-  try {
-    // m_pConf->remove(rootName) will only work in Poco v >=1.4. Current Ubuntu
-    // and RHEL use 1.3.x
-    // Simulate removal by marking with a flag value
-    m_pConf->setString(rootName, m_removedFlag);
-  }
-  catch (Poco::NotFoundException &) {
-    g_log.debug() << "Unable to find " << rootName << " in the properties file"
-                  << std::endl;
-  }
+  m_pConf->remove(rootName);
   m_changed_keys.insert(rootName);
 }
 
@@ -1059,9 +1026,7 @@ void ConfigServiceImpl::remove(const std::string &rootName) const {
  *  @returns Boolean value denoting whether the exists or not.
  */
 bool ConfigServiceImpl::hasProperty(const std::string &rootName) const {
-  // Work around a limitation of Poco < v1.4 which has no remove functionality
-  return m_pConf->hasProperty(rootName) &&
-         m_pConf->getString(rootName) != m_removedFlag;
+  return m_pConf->hasProperty(rootName);
 }
 
 /** Checks to see whether the given file target is an executable one and it