Replace memset 0 with initializers.

Test: Compiles and bionic unit tests pass.
Change-Id: I94e178c56d958beeb1c484e4d52d61df022189e8
diff --git a/tests/unistd_test.cpp b/tests/unistd_test.cpp
index 9ad3b6d..3143c23 100644
--- a/tests/unistd_test.cpp
+++ b/tests/unistd_test.cpp
@@ -1393,9 +1393,7 @@
 }
 
 TEST(UNISTD_TEST, setdomainname) {
-  __user_cap_header_struct header;
-  memset(&header, 0, sizeof(header));
-  header.version = _LINUX_CAPABILITY_VERSION_3;
+  __user_cap_header_struct header = {.version = _LINUX_CAPABILITY_VERSION_3};
 
   __user_cap_data_struct old_caps[_LINUX_CAPABILITY_U32S_3];
   ASSERT_EQ(0, capget(&header, &old_caps[0]));