msfdb fails to init database if msfconsole hasn't been run

[jhart-r7]

Depending on how metasploit was installed, or what was run after install, the ~/.msf4 directory will not exist.

For example, if you use this installer and don't run msfconsole, the ~/.msf4 directory will not exist (assuming an otherwise clean system). Normally this isn't a problem, because when you then run msfconsole (as non-root), it will prompt you to create the database, and at that point ~/.msf4 will have been created and all is well.

However, if you are attempting to run msfconsole, say, with an RC file or other ~unattended fashion, the prompting may not happen or may not be desirable. In these situations, one could run msdb init, but because ~/.msf4 doesn't exist, you will encounter the following:

/opt/metasploit-framework/embedded/framework/msfdb:210:in `initialize': No such file or directory @ rb_sysopen - /home/msf/.msf4/database.yml (Errno::ENOENT)
	from /opt/metasploit-framework/embedded/framework/msfdb:210:in `open'
	from /opt/metasploit-framework/embedded/framework/msfdb:210:in `init_db'
	from /opt/metasploit-framework/embedded/framework/msfdb:315:in `<main>'

Until I read the code, I chased my tail a bit trying to find a database.yml that would work, and was confused because there wasn't one that came with the installer. As it turns out, the issue is as I described above.

This is a simple fix. PR incoming.

My simple work around locally was to mkdir ~/.msf4 prior to msfdb init, which #62 implements more officially.

[0x00eh]

$ sudo msfconsole