Use test.base's get_rand_name function to ensure that bridge name
lengths don't exceed the maximum device name length. For uses that
require multiple bridges/ports with the same random characters
appended, add get_related_rand_names and get_related_rand_device_names
functions.
Change-Id: Ib03653f3ca2d2c3d2ea7be1dff4ab0e4e77df51e
Closes-Bug: #1561152