log/syslog: skip unsupported tests on iOS
log/syslog: skip unsupported tests on iOS

CL 193843 disabled sysctl on iOS. This change disables two tests that
rely on sysctl.

Updates #34133

Change-Id: I7c569a1992a50ad6027a294c1fd535cccddcfc4e
Reviewed-on: https://go-review.googlesource.com/c/go/+/193844
Run-TryBot: Elias Naur <1d6e1cf70ec6f9ab28d3ea4b27a49a77654d370e@eliasnaur.com>
Reviewed-by: Tobias Klauser <0a68dd4915066ec5d3f81f75a828fee53dcc8822@gmail.com>

golang/go,nawawi/go,CAFxX/go,golang/go,akutz/go,akutz/go,CAFxX/go,nawawi/go,akutz/go,nawawi/go,nawawi/go,cloudflare/go,akutz/go,cloudflare/go,cloudflare/go,CAFxX/go,golang/go,nawawi/go,golang/go,akutz/go,nawawi/go,golang/go,cloudflare/go,cloudflare/go,CAFxX/go,cloudflare/go,golang/go,cloudflare/go,nawawi/go,golang/go,nawawi/go,akutz/go,CAFxX/go,CAFxX/go,cloudflare/go,CAFxX/go,golang/go,akutz/go,CAFxX/go,akutz/go