refactor(qns): use -v command line flag

mozilla#1692 introduced verbosity command line
flags in `neqo-server` and `neqo-client`.

This commit makes use of the flags instead of the `RUST_LOG` environment variable.

qns/interop.sh

@@ -12,7 +12,7 @@ export PATH="${PATH}:/neqo/bin"
 case "$ROLE" in
 client)
   /wait-for-it.sh sim:57832 -s -t 30
-  RUST_LOG=debug RUST_BACKTRACE=1 neqo-client --cc cubic --qns-test "$TESTCASE" \
+  RUST_BACKTRACE=1 neqo-client -v --cc cubic --qns-test "$TESTCASE" \
     --qlog-dir "$QLOGDIR" --output-dir /downloads $REQUESTS 2> >(tee -i -a "/logs/$ROLE.log" >&2)
   ;;
 
@@ -26,7 +26,7 @@ server)
     -name "$CERT" -passout pass: -out "$P12CERT"
   pk12util -d "sql:$DB" -i "$P12CERT" -W ''
   certutil -L -d "sql:$DB" -n "$CERT"
-  RUST_LOG=info RUST_BACKTRACE=1 neqo-server --cc cubic --qns-test "$TESTCASE" \
+  RUST_BACKTRACE=1 neqo-server -v --cc cubic --qns-test "$TESTCASE" \
     --qlog-dir "$QLOGDIR" -d "$DB" -k "$CERT" '[::]:443' 2> >(tee -i -a "/logs/$ROLE.log" >&2)
   ;;