test1474: make precheck more robust on non-Solaris systems

If uname -r returns something odd, perl could return an error code and
the test would be erroneously skipped. The qx// syntax avoid this.

Followup to 08f9b21

tests/data/test1474

@@ -89,7 +89,7 @@ HTTP PUT with Expect: 100-continue and 417 response during upload
 http://%HOSTIP:%HTTPPORT/we/want/%TESTNUMBER -T %LOGDIR/test%TESTNUMBER.txt --limit-rate 64K --expect100-timeout 0.001
 </command>
 <precheck>
-perl -e "print 'Test does not work on this BSD system' if ( $^O eq 'netbsd' || $^O eq 'openbsd' || ($^O eq 'solaris' && `uname -r` * 100 <= 510));"
+perl -e "print 'Test does not work on this BSD system' if ( $^O eq 'netbsd' || $^O eq 'openbsd' || ($^O eq 'solaris' && qx/uname -r/ * 100 <= 510));"
 </precheck>
 # Must be large enough to trigger curl's automatic 100-continue behaviour
 <file name="%LOGDIR/test%TESTNUMBER.txt">