CI/travis/lib.sh: ensure sudo exists (in docker env)
CI/travis/lib.sh: ensure sudo exists (in docker env)

Docker images may not have sudo installed, so make sure it is.

Signed-off-by: Alexandru Ardelean <685557f6b7c225d86b536740313ed51b24843a58@analog.com>

analogdevicesinc/libiio,analogdevicesinc/libiio,analogdevicesinc/libiio,analogdevicesinc/libiio