netd: use PLOG where appropriate.

Also, libbase logging promises not to clobber errno, so you don't need
to save/restore errno around logging calls (because that would be a huge
pain).

Test: builds
Change-Id: I9315fc885c7cf224a4f22fd4746f57931f6d556f
diff --git a/resolv/res_cache.cpp b/resolv/res_cache.cpp
index a38fc4c..ad5a2c5 100644
--- a/resolv/res_cache.cpp
+++ b/resolv/res_cache.cpp
@@ -1016,13 +1016,12 @@
                         result = ttl;
                     }
                 } else {
-                    LOG(INFO) << "ns_parserr failed ancount no = " << n
-                              << ". errno = " << strerror(errno);
+                    PLOG(INFO) << "ns_parserr failed ancount no = " << n;
                 }
             }
         }
     } else {
-        LOG(INFO) << "ns_initparse failed: " << strerror(errno);
+        PLOG(INFO) << "ns_initparse failed";
     }
 
     LOG(INFO) << "TTL = " << result;