libsysutils: Add string.h to includes

Signed-off-by: San Mehat <san@google.com>
diff --git a/libsysutils/src/FrameworkListener.cpp b/libsysutils/src/FrameworkListener.cpp
index bbf3f3a..b920215 100644
--- a/libsysutils/src/FrameworkListener.cpp
+++ b/libsysutils/src/FrameworkListener.cpp
@@ -14,6 +14,7 @@
  * limitations under the License.
  */
 #include <errno.h>
+#include <string.h>
 
 #define LOG_TAG "FrameworkListener"