mkuserimg_mke2fs: fix empty -E to mke2fs and empty -S to e2fsdroid

not passing in -s caused a -E to be passed to mke2fs without any options
not passing in FILE_CONTEXTS caused a -S to be passed to e2fsdroid
without a file

Test: build oem image (doesn't pass in -s or [FILE_CONTEXTS])
Change-Id: Id00ca79b6b5fdc75e603ab568d74f1a183f8e56b
Signed-off-by: Ben Fennema <fennema@google.com>
1 file changed