False error message for concurrent mounts

When a CVMFS-repo is already mounted at e.g. /mnt/a and one tries to mount it again at /mnt/b, the error message is:

Repository XXX is already mounted on /mnt/b

instead of

Repository XXX is already mounted on /mnt/a

The error is obvious in:
https://github.com/cvmfs/cvmfs/blob/baa5abdd6b5ecb8a4fa34032e9832c3c44ace54b/mount/mount.cvmfs.cc#L354

The error message uses the string mountpoint which is the mountpoint of the new, attempted mount.
The actual old mountpoint is however queried in CheckConcurrentMount at
https://github.com/cvmfs/cvmfs/blob/baa5abdd6b5ecb8a4fa34032e9832c3c44ace54b/mount/mount.cvmfs.cc#L142
but the string mountpoint used there is a local variable, which is thrown away after querying it.

Cheers,

Oliver