TT#8635 set umask for files created by docker

tests made in 'docker run' create files with 'root' owner and ws-cleanup
plugin can't delete them after. Fixing umask here to allow files
deletion.

Change-Id: Ia9b03983d174a1546631f5b42e605235809711ef

t/Dockerfile

@@ -20,6 +20,11 @@ RUN echo 'prove -I /code/lib -v --color -l --formatter TAP::Formatter::JUnit' >>
 RUN echo 'prove -I /code/lib --color -l' >>/root/.bash_history
 RUN echo './t/testrunner' >>/root/.bash_history
 
+# Create files with mode 666 and folders with mode 777 which
+# allows to delete the temporary files (aka results) for
+# non-root users (like 'jenkins' or 'developer's laptop local user')
+RUN echo 'umask 0' >>/root/.bashrc
+
 WORKDIR /code/
 
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