application.getUrlForApp ignores basePath

[mshustov]

changes in application.getUrlForApp
fdd87e0#diff-1ab7c26e3c5a0d226f771d13620db1e3L141
lead to regression: #57205

As a part of bug fix, we could evaluate how much work requires to setup FTR with basePath to test the scenario properly.

[elasticmachine]

Pinging @elastic/kibana-platform (Team:Platform)

[pgayvallet]

Fix is straightforward, adapting the FTR config to use a basePath is not. As this is a regression and should lands in 7.6.1 I created a PR with the simple fix.