install-hydra.sh: Fix install when the /usr/local/bin/hydra exists
install-hydra.sh: Fix install when the /usr/local/bin/hydra exists

Step1:

user1 installs hydra
/usr/local/bin/hydra -> /home/user1//scylla-cluster-tests/docker/env/hydra.sh

Step2:

user2 installs hydra
/usr/local/bin/hydra -> /home/user1/scylla-cluster-tests/docker/env/hydra.sh

user2 will use the install from user1.

To fix create the link with -f option and unconditionally.

To make it even better, we'd better create the link under ~/.local/bin not /usr/local/bin.

scylladb/scylla-cluster-tests,scylladb/scylla-cluster-tests,scylladb/scylla-cluster-tests,scylladb/scylla-longevity-tests,scylladb/scylla-cluster-tests,scylladb/scylla-longevity-tests,scylladb/scylla-longevity-tests,scylladb/scylla-cluster-tests