fixes ExecStart systemd's option for node control tool (#650)
fixes ExecStart systemd's option for node control tool (#650)

* removes square brackets for optional argument from ExecStart

see "Basic environment variable substitution is supported" part in
https://www.freedesktop.org/software/systemd/man/systemd.service.html#Command%20lines

Signed-off-by: Andrey Kononykhin <f5093be107643eb8c00140436c928dc99d5ca857@gmail.com>

* removes unnecessary quotes in ExecStart

Signed-off-by: Andrey Kononykhin <f5093be107643eb8c00140436c928dc99d5ca857@gmail.com>

spivachuk/sovrin-node,spivachuk/sovrin-node,spivachuk/sovrin-node,spivachuk/sovrin-node