Adding a script to check if a file exists on cvmfs after uploading

[calcuttj]

dune-justin$ ./commands/justin-check-cvmfs -p /cvmfs
Path: /cvmfs
N Checks: 10

Attempt 1/10...
Found


dune-justin$ ./commands/justin-check-cvmfs -p /asdf -n 3
Path to check: /asdf
Will check 3 times
Path: /asdf
N Checks: 3

Attempt 3/3...
Could not find