If the leases.txt file was not present on the system, coredhcp would
fail to start --
level=info msg="DHCPv4: loading plugin `range`" prefix=plugins
level=warning msg="Failed to close file leases.txt: invalid argument" prefix="plugins/range"
level=fatal msg="cannot open lease file leases.txt: open leases.txt: no such file or directory" prefix=main
This changes the call to include the O_CREATE flag to create the leases file if it does not already exist.
Signed-off-by: Brad Beam <email@example.com>