perftune.py executes hwloc-calc, the command is now provided as
relocatable binary, placed under /opt/scylladb/bin.
So we need to add the directory to PATH when calling
subprocess.check_output(), but our utility function already do that,
switch to it.
Fixes#4443
Signed-off-by: Takuya ASADA <syuu@scylladb.com>
Message-Id: <20190418124345.24973-1-syuu@scylladb.com>