cluster/afr: Change Self-heal domain separator to ':'

'-' can be present in a volume. This may lead to domain
collisions in future.

Tests:
Checked in gdb that domain comes with ':' separator:

Breakpoint 1, pl_common_inodelk (frame=0x7fdabcce51a4,
this=0x8bde20, volume=0x8b50d0 "r2-replicate-0:self-heal",
inode=0x7fdab822f0e8, cmd=6, flock=0x7fdabc76eee4,
loc=0x7fdabc76ede4, fd=0x0, xdata=0x7fdabc6e0ab0) at inodelk.c:597

Change-Id: I4456ae35ac8bf21e6361c34e9ad437f744a2e84b
BUG: 993981
Signed-off-by: Pranith Kumar K <pkarampu@redhat.com>
Reviewed-on: http://review.gluster.org/6025
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>
Tests: Enable fore-ground self-heal

Change-Id: Ibfca8ddb7c663d44ed447be13b2eabb7bd393bb3
BUG: 993981
Signed-off-by: Pranith Kumar K <pkarampu@redhat.com>
Reviewed-on: http://review.gluster.org/6028
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>