Use "$*" instead of "$@" in tox_install.sh

Checking for no arguments via

[ -z "$@" ]

works if there's zero or one arguments, but breaks if there's more than
one:

[: too many arguments

Checking via

[ -z "$*" ]

does not suffer this malady.

Co-Authored-By: Elod Illes <elod.illes@ericsson.com>

Change-Id: Ieb36a775c6a1db027e0be684851582265fbb5f48

tools/tox_install.sh

@@ -55,7 +55,7 @@ fi
 # install will be constrained and we need to unconstrain it.
 edit-constraints $localfile -- $LIB_NAME "-e $LIB_LOCATION"
 
-if [ -z "$@" ]; then
+if [ -z "$*" ]; then
     echo "No packages to be installed."
     exit 0
 fi