scripts/test-remote-image: add value check for rootfs fstype, change method name...

scripts/test-remote-image: add value check for rootfs fstype, change method name used.

As per change in the oeqa/targetcontrol.py's BaseTarget class, changing the use of get_image_fstype() to match_image_fstype().

Also because there is no longer a value check done by the target controller's match_image_fstype() method, we have to do one here.

+ one helper comment for the get_controller() method.

Signed-off-by: Corneliu Stoicescu <corneliux.stoicescu@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>