Fix check for options in "command alias"

Summary:
"command alias" can add invalid options to the command. "command alias start process launch -s" will add an extra argument, "<no-argument>" to the alias, so it runs "process launch -s <no-argument>", which launches the process with args that include "<no-argument>".

This patch changes the text compare of the variable value with "<OptionParser::eNoArgument>" to a compare of variable value_type with OptionParser::eNoArgument. It also moves the previous test inside the if, so it won't add a trailing space if there is no argument.

Reviewers: clayborg

Reviewed By: clayborg

Subscribers: lldb-commits

Differential Revision: http://reviews.llvm.org/D8844

llvm-svn: 234244