REGTEST: make check_condition.vtc fail as soon as possible

The test consists in a sequence of shell commands, but the shell is not
necessarily started with strict errors enabled, so only the last command
provides the verdict. Let's add "set -e" to make it fail on the first
test that fails.

reg-tests/startup/check_condition.vtc

@@ -3,6 +3,7 @@ varnishtest "Tests the -cc argument"
 feature cmd "$HAPROXY_PROGRAM -cc 'version_atleast(2.5-dev0)'"
 
 shell {
+    set -e
     $HAPROXY_PROGRAM -cc "version_atleast(2.4)"
     ! $HAPROXY_PROGRAM -cc "version_atleast(1024)"