Fix multinest temporary directory functionality

There was a bug in the current implementation of the temporary directory functionality with multinest that didn't allow successful file transfer. This meant that progress was lost at the end of the job when running through condor, and you couldn't restart either. This MR should fix the issue. I have tested it on condor.

bilby/core/sampler/pymultinest.py

@@ -181,11 +181,15 @@ class Pymultinest(NestedSampler):
                 self.outputfiles_basename, self.temporary_outputfiles_basename
             )
         )
-        if os.path.islink(self.outputfiles_basename.strip("/")):
-            os.unlink(self.outputfiles_basename.strip("/"))
-        elif os.path.isdir(self.outputfiles_basename):
-            shutil.rmtree(self.outputfiles_basename, ignore_errors=True)
-        shutil.move(self.temporary_outputfiles_basename, self.outputfiles_basename)
+        if self.outputfiles_basename.endswith('/'):
+            outputfiles_basename_stripped = self.outputfiles_basename[:-1]
+        else:
+            outputfiles_basename_stripped = self.outputfiles_basename
+        if os.path.islink(outputfiles_basename_stripped):
+            os.unlink(outputfiles_basename_stripped)
+        elif os.path.isdir(outputfiles_basename_stripped):
+            shutil.rmtree(outputfiles_basename_stripped)
+        shutil.move(self.temporary_outputfiles_basename, outputfiles_basename_stripped)
 
     def run_sampler(self):
         import pymultinest