Import flows should also check main

Description of problem:

Since many GH repos have changed from master to main, we are now having problem because our Import flows sets the default branch to master. We should be checking for either master or main.

This applies to:
Import from Git / Dockerfile / Devfile

Although there is a workaround to use Adv Git Options, these flows fail, and the user has no knowledge as to why.

Additional info:

This should also be backported