[bug]screencap cammand got black image in folded phone's small screen like "Oppo find N". Add a parameter to make it compatible.

[ahchchxx]

appium-uiautomator2-server/app/src/main/java/io/appium/uiautomator2/utils/ScreenshotHelper.java

Line 96 in 6b862b4

ParcelFileDescriptor pfd = automation.executeShellCommand("screencap -p");

When using folded phone, I can get screenshot image at the bigger monitor. But I can only get back image at the small screen(the bigger one is folded).
Add a parameter " -d 0" to the following command:

screencap -d 0 -p