display a better message for cb* command lines if they need sudo access

if the user tries to run ./cbenable_core_dumps.sh without sudo access it fails with this error which is very hard to decode for the user :

[ec2-user@ip-10-34-37-212 bin]$ ./cbenable_core_dumps.sh /tmp
core_pattern couldn't be set, tried: /tmp/core.%e.%p

or if the user tries to run cbbackup as a non-root user it will print
unable to open database file