always read version on startup

DONOT store this variable in qgsettings. A new/updated install of otb in
same location will mislead users

otb/OTBAlgorithmProvider.py

@@ -204,12 +204,7 @@ class OTBAlgorithmProvider(QgsProcessingProvider):
                                                 OTBUtils.geoidFile(),
                                                 valuetype=Setting.FOLDER
                                                 ))
-        ProcessingConfig.addSetting(Setting(group, OTBUtils.VERSION,
-                                                self.tr("version"),
-                                                OTBUtils.version(),
-                                                valuetype=str,
-                                                hidden=True
-                                                ))
+
         ProcessingConfig.readSettings()
         self.refreshAlgorithms()
         return True
@@ -253,8 +248,21 @@ class OTBAlgorithmProvider(QgsProcessingProvider):
         if not self.canBeActivated():
             return
 
-        if self.version is None:
-           self.version = OTBUtils.version()
+        self.version = None
+        # install_dir #otb issue 1557
+        version_file = os.path.join(OTBUtils.otbFolder(), 'share', 'doc', 'otb', 'VERSION')
+        if not os.path.isfile(version_file):
+            version_file = os.path.join(OTBUtils.otbFolder(), 'share', 'doc', 'OTB-6.6', 'VERSION')
+        if not os.path.isfile(version_file):
+            version_file = os.path.join(OTBUtils.otbFolder(), 'VERSION')
+
+        if os.path.isfile(version_file):
+            with open(version_file) as vf:
+                vlines = vf.readlines()
+                vlines = [l.strip() for l in vlines]
+                vline = vlines[0]
+                if 'OTB Version:' in vline:
+                    self.version = vline.split(':')[1].strip()
 
         QgsMessageLog.logMessage(self.tr("Loading OTB '{}'.".format(self.version)), self.tr('Processing'), Qgis.Info)        
         self.algs = self.createAlgsList()