init: Enable ANDROID_BASE_UNIQUE_FD_DISABLE_IMPLICIT_CONVERSION

From the unique_fd.h header file: "unique_fd's operator int is
dangerous, but we have way too much code that depends on it, so make
this opt-in at first."

From the Google C++ style guide: "Do not define implicit conversions."
See also go/cstyle#Implicit_Conversions.

Hence this CL that disables unique_fd::operator int().

Change-Id: I28d94755d5408f63e5819da8d1cbc285057f867f
Signed-off-by: Bart Van Assche <bvanassche@google.com>
diff --git a/init/util.cpp b/init/util.cpp
index 3d42855..bc8ea6e 100644
--- a/init/util.cpp
+++ b/init/util.cpp
@@ -120,12 +120,12 @@
 
     if (passcred) {
         int on = 1;
-        if (setsockopt(fd, SOL_SOCKET, SO_PASSCRED, &on, sizeof(on))) {
+        if (setsockopt(fd.get(), SOL_SOCKET, SO_PASSCRED, &on, sizeof(on))) {
             return ErrnoError() << "Failed to set SO_PASSCRED '" << name << "'";
         }
     }
 
-    int ret = bind(fd, (struct sockaddr *) &addr, sizeof (addr));
+    int ret = bind(fd.get(), (struct sockaddr*)&addr, sizeof(addr));
     int savederrno = errno;
 
     if (!secontext.empty()) {
@@ -145,7 +145,7 @@
     if (fchmodat(AT_FDCWD, addr.sun_path, perm, AT_SYMLINK_NOFOLLOW)) {
         return ErrnoError() << "Failed to fchmodat socket '" << addr.sun_path << "'";
     }
-    if (should_listen && listen(fd, /* use OS maximum */ 1 << 30)) {
+    if (should_listen && listen(fd.get(), /* use OS maximum */ 1 << 30)) {
         return ErrnoError() << "Failed to listen on socket '" << addr.sun_path << "'";
     }
 
@@ -168,7 +168,7 @@
     // For security reasons, disallow world-writable
     // or group-writable files.
     struct stat sb;
-    if (fstat(fd, &sb) == -1) {
+    if (fstat(fd.get(), &sb) == -1) {
         return ErrnoError() << "fstat failed()";
     }
     if ((sb.st_mode & (S_IWGRP | S_IWOTH)) != 0) {