Fix test code to can be built on alpine

Signed-off-by: joseph <[email protected]>

ChangeLog.d/do-not-use-obsolete-header.txt

@@ -0,0 +1,5 @@
+Bugfix
+   * Don't use the obsolete header path sys/fcntl.h in unit tests.
+     These header files cause compilation errors in musl.
+     Fixes #4969.
+

tests/suites/test_suite_net.function

@@ -9,11 +9,11 @@
 #endif
 
 #if defined(MBEDTLS_PLATFORM_IS_UNIXLIKE)
-#include <sys/fcntl.h>
 #include <sys/resource.h>
 #include <sys/stat.h>
 #include <sys/time.h>
 #include <sys/types.h>
+#include <fcntl.h>
 #include <unistd.h>
 #endif