fs_mgr: Adding logs when failing to wait for a device file

During mount operations, fs_mgr_wait_for_file() is invoked to
ensure the device file exists before starting to mount it. Adding
logs when the wait fails and also skip mounting as it won't be
successful. Also merge fs_mgr_test_access() and wait_for_file()
as fs_mgr_wait_for_file().

Test: Boot device and manually trigger the timeout issue
Test: Check and confirm whether timeout log info is inside ksmg.

Change-Id: Ide6d7fdca41e03e169e4400f91b7dea327985aaf