feat: add disable cloneurl check flag

[philslab-ninja]

what

Adding a new flag to optionally disable the clone URL path check that verifies the clone URL matches the repo name

why

In one of my projects github enterprise unfortunately was setup with a basepath (like git.acme.com/gitlab). Setting ATLANTIS_GITLAB_HOSTNAME to git.acme.com/gitlab results in an error like:
expected clone url to have path "/path/to/repo.git" but had "/gitlab/path/to/repo.git"

Setting the new flag to true disables this check

tests

• I have tested my changes by building atlantis and running it with the new flag

references

closes #1450

[philslab-ninja]

as discussed in slack a simpler aproach is desired without the need for another flag