Remove extra quote from the mysqldump password argument

The mysqldb Ansible module will fail if the state specified is import or dump with a '1045: Access Denied' mysql error for complex passwords.

This is caused by the extra quote around the '--password' argument to mysqldump, as pipes.quotes already quotes the password string.

>>> "--password='%s'" % pipes.quote('simple')
"--password='simple'"

>>> "--password='%s'" % pipes.quote('c0mplexp@ssword!')
"--password=''c0mplexp@ssword!''"

>>> "--password='%s'" % pipes.quote('password with space')
"--password=''password with space''"