1.Android4.4在解析jpg头的时候使用的库不支持多线程，造成拷贝大量jpg文件的时候出错.
step to reproduce.
a. Connect PC & DUT via USB cable.
b. Settings -> Storage, check with MTP mode.
c.copy jpg files to the device.Total size is about 100M.
Actual result :Sometimes, the copy will fail.
2.Android4.4 GMS Camera有问题，4.4的GMS camera应用拍照以后jpg文件的实际大小和mtp database中的大小不一致，导致预览的时候可能出问题，解决预览的问题又会导致上面这个问题
step to reproduce
a. Connect PC & DUT via USB cable.
b. Settings -> Storage, check with MTP mode.
c. Open DUT folder on PC, then try to open a camera captured picture file.
d. Also test with PTP mode.
Actual result : It takes long time to load picture file or sometimes it failed to load picture file