test: don't print backtrace when errexit is off

Some test scripts may temporarily disable errexit -
for example, trying a command several times until
it succeeds.  In these cases we don't want to
print a backtrace every time that command fails.

Signed-off-by: Jim Harris <james.r.harris@intel.com>
Change-Id: I481f50b046eb13e23f7048672281ec7d62a573a2

Reviewed-on: https://review.gerrithub.io/423921
Chandler-Test-Pool: SPDK Automated Test System <sys_sgsw@intel.com>
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Ben Walker <benjamin.walker@intel.com>
Reviewed-by: Pawel Wodkowski <pawelx.wodkowski@intel.com>
Reviewed-by: Shuhei Matsumoto <shuhei.matsumoto.xt@hitachi.com>

test/common/autotest_common.sh

@@ -439,6 +439,9 @@ function run_test() {
 }
 
 function print_backtrace() {
+	# if errexit is not enabled, don't print a backtrace
+	[[ "$-" =~ e ]] || return 0
+
 	local shell_options="$-"
 	set +x
 	echo "========== Backtrace start: =========="