[E2E] Fix bug in expandPathAndOpenFile

[Katka92]

In upstream, there is a bug while using method expandPathAndOpenFile of ProjectTree.ts. The issue is that the wrong css path is generated, it includes two slashes instead of one. Was: /projects:/projects//console-java-simple, should be: /projects:/projects/console-java-simple.
I've created PR with the fix in upstream [1], but it will not be included to 7.1.0 version, so we need to create a workaround on our side too.

This is a part of fixing incompatible changes for 7.1.0 version #1575

[1] eclipse-che/che#14435

[Katka92]

The workaround was created on Rh-Che side as a part of fixing 7.1.0 issues. This workaround should be removed when 7.2 is released.