Images: don't put pelican binaries into /pelican

[matyasselmeci]

We had one site bind-mount their storage dir over /pelican, which caused an error at startup because the binaries were no longer there.

We do not prescribe a location for where data should be mounted, and IMO /pelican is a perfectly reasonable choice; we should avoid the issue by moving the binaries to some different location.

It is good practice to follow the Filesystem Hierarchy Standard, even in containers. The pelican and osdf binaries should be moved into /usr/local/bin.