envsetup.sh: partly fix syswrite

The grep doesn't work because "Reboot" is capitalized in the
enable-verity output. Now, syswrite gets farther, but fails before the
final remount.

    $ syswrite
    adbd is already running as root
    Successfully disabled verity
    Enabled overlayfs
    rebooting
    restarting adbd as root
    error: closed

Test: ran syswrite on freshly flashed device
Change-Id: I26aaa6278d76dcab56fd4bde3d70ac7841ae2a3b