*: Use -n instead of ! -z. [SC2236]

Signed-off-by: Sam Batschelet <sbatsche@redhat.com>

test

@@ -115,7 +115,7 @@ fi
 
 # determine the number of CPUs to use for Go tests
 TEST_CPUS="1,2,4"
-if [ ! -z "${CPU}" ]; then
+if [ -n "${CPU}" ]; then
 	TEST_CPUS="${CPU}"
 fi
 echo "Running with TEST_CPUS:" "${TEST_CPUS}"
@@ -126,7 +126,7 @@ if [ "$GOARCH" == "amd64" ]; then
 fi
 
 RUN_ARG=""
-if [ ! -z "${TESTCASE}" ]; then
+if [ -n "${TESTCASE}" ]; then
 	RUN_ARG="-run=${TESTCASE}"
 fi
 
@@ -381,7 +381,7 @@ function shellcheck_pass {
 function markdown_you_pass {
 	# eschew you
 	yous=$(find . -name \*.md ! -path './vendor/*' ! -path './Documentation/v2/*' ! -path './gopath.proto/*' -exec grep -E --color "[Yy]ou[r]?[ '.,;]" {} + || true)
-	if [ ! -z "$yous" ]; then
+	if [ -n "$yous" ]; then
 		echo -e "found 'you' in documentation:\\n${yous}"
 		exit 255
 	fi
@@ -413,13 +413,13 @@ function goword_pass {
 		gofiles=($gofiles)
 		# only check for broken exported godocs
 		gowordRes=$(goword -use-spell=false "${gofiles[@]}" | grep godoc-export | sort)
-		if [ ! -z "$gowordRes" ]; then
+		if [ -n "$gowordRes" ]; then
 			echo -e "goword checking failed:\\n${gowordRes}"
 			exit 255
 		fi
 		# check some spelling
 		gowordRes=$(goword -ignore-file=.words clientv3/{*,*/*}.go 2>&1 | grep spell | sort)
-		if [ ! -z "$gowordRes" ]; then
+		if [ -n "$gowordRes" ]; then
 			echo -e "goword checking failed:\\n${gowordRes}"
 			exit 255
 		fi
@@ -663,7 +663,7 @@ function dep_pass {
 	badpkg="(etcdserver$|mvcc$|backend$|grpc-gateway)"
 	deps=$(go list -f '{{ .Deps }}'  | sed 's/ /\n/g' | grep -E "${badpkg}" || echo "")
 	popd >/dev/null
-	if [ ! -z "$deps" ]; then
+	if [ -n "$deps" ]; then
 		echo -e "clientv3 has masked dependencies:\\n${deps}"
 		exit 255
 	fi