Provide a way to select a default Jira instance if none is set

[DHaussermann]

If the user connects to multiple Jira instances and does not yet create an issue, no default instance will be set yet. This causes some commands to fail which use the default instance if none is passed in. fir example:

• /jira transition DP-44 done
• /jira instance settings list

The feedback is bad and suggests a problem has occurred. We should tell the user no default instance is set and possibly a way to select one.

Steps:

• Login as a test user
• Connect to 2 installed Jira instances
• Do not create and issue or attach so, user has no default instance
• type /jira instance settings list
  Observed:

[catalintomai]

Please fix the error message: "Please provide an instance, since no instance is being set currently", cc: @aaronrothschild. @DHaussermann : please open ticket for setting the instance without needing to use the create modal, etc.