[mb2] Increment build release number in spec every time an RPM is built

Signed-off-by: Juha Kallioinen <juha.kallioinen@jolla.com>
[mb2] Handle errors in deploy phase more gracefully

Additionally the rpm file copied to the device is always
removed from the device after pkcon/zypper has been run.

Signed-off-by: Juha Kallioinen <juha.kallioinen@jolla.com>