Camera: Camera3InputStream: Stop after finding buffer to return

Erasing iterator invalidates it, so it's not safe to continue using it.
Besides, there should only be one buffer to erase anyway.

Bug: 27878949
Change-Id: I00e9845fa953c26e117e40112b9f35fc781c5dcf
diff --git a/services/camera/libcameraservice/device3/Camera3InputStream.cpp b/services/camera/libcameraservice/device3/Camera3InputStream.cpp
index 7dab2e3..f781ded 100644
--- a/services/camera/libcameraservice/device3/Camera3InputStream.cpp
+++ b/services/camera/libcameraservice/device3/Camera3InputStream.cpp
@@ -116,6 +116,7 @@
                 bufferFound = true;
                 bufferItem = tmp;
                 mBuffersInFlight.erase(it);
+                break;
             }
         }
     }