fix: only check passphrase file if set
If the REDIS_TLS_KEY_FILE_PASS environment variable is not set, do not
check to see if that file exists and do not configure it.
Signed-off-by: Travis Raines <571832+rainest@users.noreply.github.com>
Co-authored-by: Fran Mulero <fmulero@vmware.com>