scylla-sstable tries to read scylla.yaml via the following sequence:
1) Use user-provided location is provided (--scylla-yaml-file parameter)
2) Use the environment variables SCYLLA_HOME and/or SCYLLA_CONF if set
3) Use the default location ./conf/scylla.yaml
Step 3 is fine on dev machines, where the binaries are usually invoked
from scylla.git, which does have conf/scylla.yaml, but it doesn't work
on production machines, where the default location for scylla.yaml is
/etc/scylla/scylla.yaml. To reduce friction when used on production
machines, add another fallback in case (3) fails, which tries to read
scylla.yaml from /etc/scylla/scylla.yaml location.
Fixes: scylladb/scylladb#22202Closesscylladb/scylladb#22241
a21ecc3253