command_util: Fix quoting in template_loop().

command_util: Fix quoting in template_loop().

Without this additional quoting, the command usage string is incorrect
in case the template contains square brackets. For example, the usage
of the lsblob commands was printed as

	Usage: lspl [-i] [-l] [-r] t

rather than the desired

	Usage: lspl [-i] [-l] [-r] [pattern]

because the command "echo [pattern]" prints "t" since there is a
subdirectory called "t" in the source tree.