grep called with extended regular expresion when testing for UUID

At line 109 in the usbmount script.
```
elif grep -q "^[[:blank:]]*UUID=\"?$UUID\"?" /etc/fstab; then
```

grep is called with extended regular expression syntax (the \\"? expression) and so fails to match any UUID in fstab.

It should be "egrep" or "grep -E" the former is more consistant with the usage one or two lines above 