common: Fix config parsing

This commit makes following changes in parsing algorithm:
 * Any printable characters are valid as parameter name -> valid parameter name
is '[A-Z_]*'
 * Ignore 'NAME=value' entry silently -> 'NAME=value' entry is a valid entry
 * Entry 'NAME=' is valid -> Entry 'NAME=' is invalid

Change-Id: Ib541c32b94315218134265f4349407611e1afcc2
master: Remove sluggishness caused by dumping metadata.

Master, instead of dumping metadata itself, tells mfsmetarestore
to apply changes stored in changelogs since last metadata backup.
If the checksums of metadata generated by mfsmetarestore and master
don't match, master will try dumping metadata itself.

Change-Id: I31a1e9dcc208e6f4bafc137d16728acc30fef8c0