test-timesync: add first test for timesyncd conf parsing

We parse the string supplied in NTP_SERVERS during configuration under an
assert_se(). Right now we will accept pretty much anything there, but in case
we are more picky in the future, add a simple test which checks that we can
actually parse whatever is in NTP_SERVERS so that we don't fail the assertion
at runtime.

.gitignore

@@ -293,6 +293,7 @@
 /test-tables
 /test-terminal-util
 /test-time
+/test-timesync
 /test-tmpfiles
 /test-udev
 /test-uid-range