tests: ts_device_init remove useless error handling

Don't why we should deinit the empty string.

This patch prepares further refactoring.

Signed-off-by: Ruediger Meier <ruediger.meier@ga-group.nl>
tests: ts_device_init skips test if no loop support
tests: ts_scsi_debug_init must not run in a subshell

ts_skip and ts_die won't work from subshell. Now we simply use
DEVNAME and DEVICE which were still globally set in that function.
tests: quiet skip missing loop
travis-ci: minor style cleanup

Signed-off-by: Ruediger Meier <ruediger.meier@ga-group.nl>
travis-ci, do make check as root
travis-ci, make -j8 and only failing checks
tests: skip more loop problems
tests: skip ts_scsi_debug_init really quiet
tests: introduce TS_CMD_UUIDGEN (never use installed one)
travis-ci: don't update gettext
travis-ci: enable all checks again